Minimally invasive spinal fixation system and related methods

ABSTRACT

This application describes surgical instruments and implants for building a posterior fixation construct across one or more segments of the spinal column. More specifically, the application describes instruments and methods for building a posterior fixation construct across one or more segments of the spinal column in a minimally invasive fashion.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/898,713, filed Jun. 11, 2020, which is a continuation of U.S. patentapplication Ser. No. 15/896,605, filed Feb. 14, 2018, now U.S. Pat. No.10,716,600, which is a continuation of U.S. patent application Ser. No.14/631,839, filed Feb. 25, 2015, now U.S. Pat. No. 9,907,582, which iscontinuation-in-part of U.S. patent application Ser. No. 13/456,210,filed Apr. 25, 2012, now U.S. Pat. No. 9,198,698, which claims priorityfrom U.S. provisional patent application No. 61/478,658 filed on Apr.25, 2011 and U.S. provisional patent application No. 61/553,052 filed onOct. 28, 2011. The U.S. patent application Ser. No. 14/631,839 alsoclaims priority to U.S. provisional patent application No. 61/944,513filed on Feb. 25, 2014 and U.S. provisional patent application No.62/078,059 filed on Nov. 11, 2014, each of which is incorporated byreference in its entirety herein.

FIELD

The field of the invention generally relates to surgical instruments andimplants for building a posterior fixation construct across one or moresegments of the spinal column.

BACKGROUND

Spinal fixation constructs are utilized to provide stability to thespine. Most often the fixation construct is used as an adjunct to fusionsurgery during which adjacent vertebrae are prepared to facilitate bonegrowth between them, thereby eliminating motion between the vertebrae.Because motion between the vertebrae tends to inhibit bone growth, thefixation constructs are employed to prevent motion so that bone can growand achieve a solid fusion. When the position of one or more vertebraemust be adjusted to restore a more natural alignment of the spinalcolumn, the fixation construct also serves to maintain the new alignmentuntil fusion is achieved. Fixation constructs of various forms are wellknown in the art Most commonly, the fixation construct is a plateanchored to the anterior column with multiple bone anchors or aposterior fixation construct including multiple anchors and a connectingrod anchored to the posterior elements of the spine. For a posteriorfixation construct the anchors (typically pedicle screws) are anchoredinto the pedicles of each vertebra of the target motion segment. ‘Theanchors are then connected by a fixation rod that is locked to eachanchor, thus eliminating motion between the adjacent vertebrae of themotion segment The posterior fixation construct may be appliedunilaterally or bilaterally. Additionally, the posterior fixationconstruct may be applied across multiple levels or motion segments.

The fixation anchors utilized in posterior fixation constructs generallyinclude an anchor portion and a rod housing. The rod housing includes apair of upstanding arms separated by a rod channel in which the fixationrod is captured and locked. When constructing the posterior fixationconstruct the surgeon must align and seat the rod in the rod channel.This can be a challenge, particularly when one or more of the vertebraeto be connected is out of alignment leaving the associated anchor offsetvertically and/or horizontally from the remaining anchor(s) of theconstruct Constructing the posterior fixation construct under minimallyinvasive access conditions (e.g. minimizing overall incision length andmuscle stripping as compared to traditional open procedures) alsoincreases the difficulty of aligning the rod with the rod channel of theanchor.

The instruments, tools, and techniques described herein are directedtowards reducing these challenges and others associated with posteriorspinal fixation.

BRIEF DESCRIPTION OF THE DRAWINGS

Many advantages of the present invention will be apparent to thoseskilled in the art with a reading of this specification in conjunctionwith the attached drawings, wherein like reference numerals are appliedto like elements and wherein:

FIG. 1 is a perspective view of the spinal fixation anchor according toan example embodiment;

FIG. 2 is a perspective view of an implantable portion of the fixationanchor of FIG. 1 after removal of an extension guide;

FIGS. 3-4 are side and front views, respectively, of the spinal fixationanchor of FIG. 1 ;

FIG. 5 is an enlarged perspective view of the junction between theimplantable portion and extension guide of the fixation anchor of FIG. 1;

FIG. 6 is an enlarged front view of the junction region between theimplantable portion and extension guide of the fixation anchor of FIG. 1;

FIG. 7 is a side view of a breaking tool, according to an exampleembodiment;

FIG. 8 is an exploded perspective view of the breaking tool of FIG. 7 ;

FIG. 9 is a front view of the fixation anchor of FIG. 1 , after proximaljoints are broken to allow the arms to separate;

FIG. 10 is a perspective view of a guide cap for use with the fixationanchor of FIG. 1 according to one example embodiment;

FIG. 11 is another perspective view of the guide cap of FIG. 10 ;

FIG. 12 is a side view of the guide cap of FIG. 10 ;

FIG. 13 is a cross section view of the guide cap as shown in FIG. 12 ;

FIG. 14 is a perspective view of the guide cap of FIG. 10 coupled to thefixation anchor of FIG. 1 ;

FIG. 15 is a perspective view of an independent reduction tool that maybe used with the guide cap and fixation anchor of FIG. 14 ;

FIG. 16 is a front view of the independent reduction tool coupled to theguide cap and fixation anchor of FIG. 14 ;

FIG. 17 is a perspective view of a lumbar spine illustrating the use ofspinal fixation anchors of FIG. 1 with the guide cap of FIG. 10 andindependent reduction instrument of FIG. 15 to implant a two levelfixation construct, according to one example;

FIG. 18 is a perspective view of the lumbar spine of FIG. 17 after thelocking caps have been deployed and extension guides have been removedto leave the final fixation construct;

FIGS. 19-20 are perspective and side views, respectively, of a lumbarspine illustrating the use of a spinal fixation system according to oneexample embodiment;

FIG. 21 is a perspective view of an example of a guide assembly formingpart of the spinal fixation system of FIG. 19 ;

FIG. 22 is a perspective view of the distal end of the guide assembly ofFIG. 21 ;

FIGS. 23-24 are perspective views of an inner member forming part of theguide assembly of FIG. 21 , shown without the outer sleeve;

FIGS. 25-26 are sectional views of the inner member of FIG. 23 ;

FIG. 27 is a plan view of the distal end of the guide assembly of FIG.21 ;

FIGS. 28-29 are perspective views of an example of a pedicle screwforming part of the spinal fixation system of FIG. 19 ;

FIGS. 30-31 are perspective and plan views, respectively, of one exampleof a tulip fanning part of the pedicle screw of FIG. 28 ;

FIG. 32 is a perspective view of the guide assembly of FIG. 21 engagedwith a pedicle screw of FIG. 28 ;

FIG. 33 is a plan view of the distal end of the guide assembly of FIG.21 engaged with the tulip of FIG. 30 ;

FIG. 34 is a sectional view of the distal end of the guide assembly ofFIG. 21 engaged with the tulip of FIG. 30 ;

FIG. 35 is a plan view of a second example of a guide assembly formingpart of the spinal fixation system of FIG. 19 , shown in an unlockedconfiguration;

FIG. 36 is a plan view of the guide assembly of FIG. 35 , shown in alocked configuration;

FIG. 37 is a plan view of the distal end of the guide assembly of FIG.35 ;

FIGS. 38-39 are plan and perspective views, respectively, of a secondexample of a tulip forming part of the pedicle screw of FIG. 28 ;

FIGS. 40-41 are plan and sectional views, respectively, of the distalend of the guide assembly of FIG. 35 coupled with the tulip of FIG. 38 ;

FIGS. 42-44 are plan, perspective, and exploded perspective views,respectively, of a third example of a guide assembly forming part of thespinal fixation system of FIG. 19 ;

FIG. 45 is one example of a spinal rod forming part of the spinalfixation system of FIG. 19 ;

FIGS. 46-48 are perspective, side plan, and end plan views of one end ofthe spinal rod of FIG. 45 ;

FIG. 49 is another example of a spinal rod forming part of the spinalfixation system of FIG. 19 ;

FIGS. 50-52 are perspective, side plan, and end plan views of one end ofthe spinal rod of FIG. 49 ;

FIG. 53 is a plan view of an example of an adjustable angle rod inserterconfigured for use with the spinal fixation system of FIG. 19 , shown ina first position;

FIG. 54 is a plan view of the rod inserter of FIG. 53 , shown in asecond position;

FIG. 55 is a plan view of the rod inserter of FIG. 53 coupled with aguide assembly of FIG. 21 ;

FIG. 56 is a sectional view of the rod inserter of FIG. 53 ;

FIGS. 57-58 are sectional views of the distal end of the rod inserter ofFIG. 53 ;

FIG. 59 is a plan view of one example of a fixed angle rod inserterconfigured for use with the spinal fixation system of FIG. 19 ;

FIG. 60 is a plan view of the rod inserter of FIG. 59 coupled with aguide assembly of FIG. 21 ;

FIG. 61 is a sectional view of the distal end of the rod inserter ofFIG. 59 ;

FIG. 62 is a plan view of another example of a fixed angle rod inserterconfigured for use with the spinal fixation system of FIG. 19 ;

FIG. 63 is a sectional view of the distal end of the rod inserter ofFIG. 62 ;

FIGS. 64-65 are perspective views of one example of a reductioninstrument configured for use with the spinal fixation system of FIG. 19;

FIG. 66 is a top plan view of an example of a lock screw: forming partof the spinal fixation system of FIG. 19 ;

FIG. 67 is a sectional view of the reduction instrument of FIG. 64 ;

FIG. 68 is a plan view of the reduction instrument of FIG. 64 coupledwith a guide assembly of FIG. 21 , which in turn is coupled to a pediclescrew of FIG. 28 ;

FIG. 69 is a sectional view of the distal end of the reductioninstrument of FIG. 64 coupled with the lock screw of FIG. 66 ;

FIG. 70 is a sectional view of the reduction instrument and lock screwof FIG. 69 in combination with the guide assembly and pedicle screw ofFIG. 68 upon reduction of the spinal rod and before engagement of thelock screw to the tulip;

FIGS. 71-72 are sectional views of the distal end of another example ofa reduction instrument configured for use with the spinal fixationsystem of FIG. 19 , shown coupled with a lock screw of FIG. 66 ;

FIGS. 73-74 are perspective and plan views, respectively, of thereduction instrument of FIG. 71 coupled with a lock screw of FIG. 66 ;

FIGS. 75-77 are plan views of another example of a reduction instrumentconfigured for use with the spinal fixation system of FIG. 19 ;

FIGS. 78-79 are plan and perspective views, respectively, of yet anotherexample of a reduction instrument configured for use with the spinalfixation system of FIG. 19 ;

FIG. 80 is a plan view: of the distal end of the reduction instrument ofFIG. 78 ;

FIG. 81 is a sectional view of the reduction instrument of FIG. 78 ;

FIG. 82 is a plan view of still another example of a reductioninstrument configured for use with the spinal fixation system of FIG. 19;

FIG. 83 is a plan view: of the reduction instrument of FIG. 82 coupledwith a pedicle screw of FIG. 28 ;

FIGS. 84-85 are perspective and sectional views, respectively, of thedistal end of the reduction instrument and pedicle screw combination ofFIG. 83 shown during reduction of a spinal rod;

FIG. 86 is an example of a compression instrument configured for usewith the spinal fixation system of FIG. 19 ;

FIGS. 87-88 are perspective views of another example of a compressioninstrument configured for use with the spinal fixation system of FIG. 19;

FIG. 89 is a top view of the compression instrument of FIG. 87 ;

FIG. 90 is a plan view of an example of a multi-load lock screw inserterconfigured for use with the spinal fixation system of FIG. 19 ;

FIGS. 91-93 are plan views of the lock screw inserter of FIG. 90 coupledto various numbers of lock screws;

FIG. 94 is a plan view of the lock screw inserter of FIG. 90 in use withthe guide assembly of FIG. 21 ;

FIG. 95 is a perspective view of the lock screw inserter of FIG. 90 withthe outer shaft removed for illustration;

FIG. 96 is a perspective view of the lock screw inserter of FIG. 90 withthe outer shaft and the spring shaft removed for illustration;

FIG. 97 is a perspective view of an example of a guide adjusterconfigured for use with the guide assembly of FIG. 21 ;

FIG. 98 is a perspective view of the guide adjuster of FIG. 97 coupledwith the guide assembly of FIG. 21 ;

FIGS. 99-100 are perspective and sectional views, respectively, of anexample of a tap guide for use with the spinal fixation system of FIG.19 ;

FIG. 101 is a perspective view of an example of an offset dilatorconfigured for use with the spinal fixation system of FIG. 19 ;

FIGS. 102-103 are perspective views of another example of an offsetdilator configured for use with the spinal fixation system of FIG. 19 ;

FIG. 104 is a plan view of a secondary dilator configured for use withthe spinal fixation system of FIG. 19 ;

FIGS. 105-106 are perspective views of an example of a rod inserterconfigured for use with the spinal fixation system of FIG. 19 ;

FIG. 107-108 are sectional views of the rod inserter of FIG. 105 ;

FIG. 109 is a perspective view of a compression tool forming part of acompression system according to one embodiment;

FIG. 110 is a perspective view of another compression tool forming partof the compression system of FIG. 109 ;

FIG. 111 is a perspective view of anther compression tool forming partof the compression system of FIG. 109 ;

FIG. 112 is a perspective view of the compression tool of FIG. 110 inuse;

FIGS. 113-115 are perspective views of the compression system of FIG.109 in use;

FIGS. 116-117 are perspective views of a compression instrumentaccording to another embodiment;

FIG. 118 is a plan view of the compression system of FIG. 116 ;

FIG. 119 is a perspective view of a base member and first handle memberforming part of the compression instrument of FIG. 116 ;

FIG. 120 is a perspective view of a second handle member forming part ofthe compression instrument of FIG. 116 ;

FIGS. 121-122 are perspective views of the compression instrument ofFIG. 116 in use;

FIG. 123 is a perspective view of another compression system accordingto another example embodiment;

FIG. 124 is a perspective view of the compression system of FIG. 123 ;

FIGS. 125-126 are perspective views of an extension tower forming partof the compression system of FIG. 123 ;

FIG. 127 is a perspective view of a translating rack forming part of thecompression system of FIG. 123 ;

FIG. 128 is a perspective view of a thumb key driver forming part of thetranslating rack of FIG. 127 ;

FIG. 129 is a plan view of the translating rack of FIG. 127 ;

FIG. 130 is a sectional plan view of the translating rack of FIG. 127 ;

FIG. 131 is a perspective view of a locking rack forming part of thecompression system of FIG. 23 ;

FIG. 132 is a plan view of the locking rack of FIG. 131 ;

FIG. 133 is a sectional plan view of the locking rack of FIG. 131 ;

FIG. 134-136 are perspective views of the compression system of FIG. 23in use;

FIG. 137 is a perspective view of an awl-tap combo according to oneembodiment;

FIG. 138 is a plan view of a needle and handle forming part of theawl-tap combo of FIG. 137 : FIG. 139 is a perspective view of theawl-tap combo in use;

FIG. 140-141 are perspective views of a surgical retractor according toan example embodiment;

FIG. 142 is a perspective view of a retractor arm assembly forming partof the surgical retractor of FIG. 140 ;

FIG. 143 is a perspective view of a first retractor arm forming part ofthe surgical retractor of FIG. 140 ;

FIG. 144 is a perspective view of a second retractor arm forming part ofthe surgical retractor of FIG. 140 ;

FIG. 145-146 are perspective views of the retractor arm assembly of FIG.142 ;

FIG. 147 is a perspective view of a blade release button forming part ofthe surgical retractor of FIG. 140 ;

FIG. 148 is a perspective view of an I-bolt forming part of the surgicalretractor of FIG. 140 ;

FIG. 149 is a perspective view of a actuator nut forming part of thesurgical retractor of FIG. 140 ;

FIGS. 150-151 are perspective views of a retractor blade forming part ofthe surgical retractor of FIG. 140 ;

FIG. 152 is a plan view of the retractor blade of FIG. 150 ;

FIG. 153 is a plan view of a screwdriver according to an exampleembodiment;

FIG. 154 is a perspective view of an inner sleeve forming part of thescrewdriver of FIG. 153 ;

FIG. 155 is a perspective view of the distal tip of the screwdriver ofFIG. 153 ;

FIG. 156 is a perspective view of one part of the screwdriver of FIG.155 ;

FIG. 157 is a perspective view of a central portion of the screwdriverwith a portion removed;

FIG. 158 is a perspective view of a polyaxial pedicle screw;

FIG. 159 is a perspective view of a polyaxial reduction screw;

FIG. 160 is a perspective view of a K-wire holder according to anexample embodiment;

FIG. 161 is an exploded plan view of the K-wore holder of FIG. 160 ;

FIGS. 162-163 are perspective views of a lock screw inserter accordingto an example embodiment;

FIG. 164 is a perspective view of the lock screw inserter of FIG. 162 ,with lock screws engaged;

FIG. 165 is an exploded perspective view of the lock screw inserter ofFIG. 162 ;

FIG. 166 is a sectional view of the lock screw inserter of FIG. 162 ;

FIG. 167 is a perspective view of the distal region of the lock screwinserter of FIG. 162 ;

FIG. 168 is an enlarged perspective view of a portion of the distalregion of the lock screw inserter of FIG. 162 ; and

FIG. 169 is a plan view of a series of steps in the use of the lockscrew inserter of FIG. 162 .

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Illustrative embodiments of the invention are described below. In theinterest of clarity, not all features of an actual implementation aredescribed in this specification. It will of course be appreciated thatin the development of any such actual embodiment, numerousimplementation specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure. The spinal fixation system disclosed herein boasts avariety of inventive features and components that warrant patentprotection, both individually and in combination.

The present application describes a spinal fixation system that may beutilized to form a fixation construct across one or more spinal levelsof a patient. The spinal fixation system may be especially useful informing fixation constructs across multiple spinal levels and/or spineswith alignment deformities requiring correction. The spinal fixationsystem includes bone anchors (e.g. anchors 16, 112, 206), anchor guides(e.g. 18, 116, 188, 224), rods (50, 114), and various instruments (e.g.reduction instruments, rod inserters, compression instruments, etc.)that can be used in various combinations to form the fixation construct.The spinal fixation system may be used for the installation of thefixation construct under minimally invasive conditions. That is, theoverall length of skin incisions required to install the fixationconstruct may be minimized compared to traditionally open pedicle screwprocedures. For example, the spinal fixation system includes a guidethat extends distally out of the patient when the anchor is engaged tothe spine. An elongated rod channel through the guide helps direct therod into the proper position without requiring the extended incisionsneeded to fully expose the spinal segments to be fixated.

Turning to FIGS. 1-2 , there is depicted a spinal fixation anchor 10,according to an example embodiment. The spinal fixation anchor includesintegral reduction features that may be utilized to seat a fixation rodin the anchor while realigning the position of the associated vertebrarelative to other vertebra associated with the fixation construct.Additionally, separate reduction tools that cooperate with the spinalfixation anchor may be utilized to help seat the rod and realign theassociated spinal segment. The fixation anchor 10 includes a bone anchor12 (e.g. shank with thread feature 14) suitable for stable fixation tovertebral bone and a housing 16 for capturing and locking a fixation rod50. Attached to the housing 16 is a break-off extension guide 18. Theextension guide 18 helps align the rod 50 with the housing 16 and alsohelps reduce the rod into the housing when necessary. After the rod 50is locked within housing 16 the extension guide 18 can be removed fromthe housing so the incision can be closed over the fixation construct(FIG. 2 depicts the fixation anchor with the extension guide 18completely removed).

The housing 16 has a base 20 that mates with the bone anchor 12 and apair of upstanding arms 22 a and 22 b separated by a rod channel 24. Thearms 22 a and 22 b are equipped with a locking cap guide and advancementfeature 26, such as by way of example, a helically wound flange featuredisposed on the interior face of each arm 22 a and 22 b. The locking capguide and advancement feature mates with a complementary guide andadvancement feature on a locking cap 51. The locking cap 51 engages theupstanding arms via the complementary guide and advancement features topress and lock the fixation rod 50 into the housing 16.

The housing 16 and anchor 12 may be mated with a polyaxial engagementsuch that the housing 16 can pivot relative to the anchor 12 in anydirection. The engagement may also be such that the pivoting movementmay be inhibited in one or more directions. By way of example, thehousing 16 and anchor 12 may be mated with a uniplanar engagement suchthat the housing pivots relative to the anchor 12 in a single plane. Thehousing 16 and anchor 12 may also be fixed such that no movement ispossible between the housing 16 and anchor 12.

Break-off extension guide 18 extends from the top of housing 16 andincludes a pair of extension arms 30 a and 30 b. Extension arm 30 aattaches to housing arm 22 a via an integral but breakable distal joint32 a. Extension arm 30 b attaches to housing arm 22 b via an integralbut breakable distal joint 32 b. The breakable distal joints 32 a and 32b are formed by surface grooves which reduce the material thicknessalong the entire junction between the extension arms 30 a, 30 b andhousing arms 22 a, 22 b, respectively, such that directing anappropriate force to the extension arm will snap the associatedbreakable joint. The extension arms 30 a and 30 b are dimensioned with alength such that the extension guide 18 extends from the housing 16 to alocation outside of the patient when the fixation anchor 10 is in afully implanted position and securely anchored to the vertebra. At aproximal end 34 of the extension guide 18 the extension arms 30 a and 30b come together to form a pair of integral but breakable proximal joints36. Opposed vertical surface grooves above the guide slots 38 reducematerial thickness along each junction between the extension arms 30 aand 30 b to form the breakable proximal joints 36.

Opposed guide slots 38 formed between arms 30 a and 30 b align with therod channel 24 of the anchor housing 16 to define an enclosed guidechannel 40 which is dimensioned to allow passage of a fixation rod 50.Utilizing the guide channel 40 to align the rod 50 with the housing rodchannel 24 reduces the need for fiddlesome manipulation of the housingand/or rod down near the target site, as well as the associated need tofully visualize the housing 16 during rod insertion. Thus, the overallsize of the incision required to implant a fixation construct usingfixation anchors 10 is significantly reduced compared to openprocedures. Though not necessary, after the anchor 10 is implanted, andto help facilitate rod insertion, the proximal joints 36 may be broken,thereby severing the proximal connection of the extension arms 30 a and30 b and allowing the arms 30 a and 30 b to flex apart (FIG. 9 ). Afterbreaking the proximal joints 36, a guide cap 71 (described below) may beused to reassociate the extension arms 30 a and 30 b if desired. Recess40 a on the proximal end of extension arm 30 a and recess 40 b on theproximal end of extension arm 30 b facilitate the releasable coupling ofthe guide cap 71 to the proximal end 34 of the extension guide 18.

As best pictured in FIG. 5 , the fixation anchor 10 includes an integralreduction feature which provides for effective, single step reductionand locking when the spinal alignment necessitates the rod be reducedinto the housing 16. The distal ends of extension arms 30 a and 30 b areappointed with a locking cap guide and advancement feature 42 situatedadjacent to the breakable distal joints 32 a and 32 b. The guide andadvancement feature 42 matches the guide and advancement feature 26 onthe interior face of arms 22 a and 22 b. Further, the guide andadvancement feature 42 is timed with the guide and advancement feature26 such that the locking cap 51 advances seamlessly from the extensionguide 18 to the housing 16. This configuration provides a mechanicaladvantage when advancing the locking cap 51 along the guide andadvancement features 42 and 26, allowing the locking cap 51 to drive therod into the housing 16 until it is fully seated and locked in position.

At some point during the surgical procedure after the fixation anchor(s)are anchored securely to their respective vertebra, the breakable distaljoints 32 a, 32 b and the breakable proximal joints 36 must be broken inorder to remove the break-off extension guide 18. The distal joints 32 aand 32 b are preferably broken only after the rod 50 is seated in thehousing 16 and the locking cap 51 is fully engaged. In the event theextension guide 18 is removed prematurely and a guide structure is stilldesirable (e.g. for rod insertion, locking cap engagement and/orreduction purposes), an attachment groove 39 a is formed in the housingarm 22 a and an attachment groove 39 b is formed in housing arm 22 b. Aslip on guide structure (not shown) may be advanced and releasablycoupled to the housing via the attachment grooves 39 a, 39 b. Theproximal breaking joints 36 are preferably broken first beforeattempting break the distal joints 32 a, 32 b. This may be done justprior to breaking the distal joints to remove the extension guide afterthe rod 50 is seated and the locking cap 51 fully engaged in the housing16. Alternatively, the surgeon may want to sever the connection betweenthe extension arms 30 a, 30 b at an earlier point during the procedure.By way of example, the proximal joints 36 may be severed prior to rodinsertion in order to facilitate easier rod insertion.

With reference to FIGS. 7-8 , an example embodiment of a breaking tool44 that may be utilized to break the proximal joints 36 is illustrated.The breaking tool 44 is designed to apply an outwardly directed force tothe proximal joints 36 from inside the extension guide 18. The breakingtool 44 is a cam driver and includes a handle 46, rotating drive shaft48, a cam 64 coupled to a distal end of the drive shaft 48, a hub 50,and a counter torque handle 52. The hub 50 has central cap 54 from whicha cylinder 56 extends distally and a faceted block 58 extendsproximally. The cylinder 56 has an exterior diameter that is slightlysmaller than an interior diameter of the extension guide 18 such thatthe cylinder 56 can be passed into the extension guide 18. The centralcap 54 has a diameter that is larger than the extension guide 18 suchthat the cap 54 controls the depth of insertion into the extension guide18, ensuring force is applied in the right locations (i.e. on or nearthe proximal joints 36). The faceted block 58 mates with a complementaryreceptacle 60 attached to the counter torque handle 52 to preventrotation of the hub 50 when the drive shaft 48 is operated.

A tunnel 66 dimensioned to receive a portion of the drive shaft 48therethrough extends through the hub 50 along a line offset from acenter axis of the cylinder 56. The cam 64 has a diameter that matchesapproximately the diameter of the cylinder 56 and a tunnel 68 forreceiving the drive shaft 48 that is offset from the center axis of thecam. The cam 64 is fixed to the drive shaft 48 via pin 70 such thatrotation of the drive shaft 48 causes the cam 64 to rotate relative tothe cylinder 56. When the cam 64 and cylinder 56 are aligned they canslide together into the extension guide 18. As the cam 64 is rotatedrelative to the cylinder 56 the combined diameter of the two componentsexpands, directing an outward force onto the extension arms 30 a, 30 bwhich causes the breakable proximal joints 36 to break, allowing theextension arms 30 a, 30 b to separate, as shown in FIG. 9 . With theproximal joints 36 severed, the distal breakable joints 32 a and 32 bcan be broken simply by bending the associated extension arm until thejoint snaps. This can be done using a common grasping tool, such asforceps for example, or grasping the extensions arms directly with thehand.

While breaking the proximal joints 36 may have desirable consequencesprior to and during rod insertion, it may also be desirable to have therigidity associated with the unbroken guide extension 18 at later pointsduring the surgery. To this end, a guide cap 71 is provided which may beused to hold the arm extensions 30 a and 30 b together and restore therigidity of the unbroken guide extension 18. The guide cap 71 has a body72 with a first internal cavity 73 opening out to a distal end 74 and asecond internal cavity 76 opening out to a proximal end 78. The firstinternal cavity 73 has an internal diameter that is just larger than theexternal diameter of the extension guide 18 such that the proximal endof the extension guide may be received in the first internal cavity 73.The second internal cavity 76 has a diameter smaller than the firstinternal cavity 73, to provide a shelf for spring 88, approximating theinternal diameter of the extension guide 18 and large enough to pass alocking cap 51 therethrough. A pair of opposed projections 80 extendinto the first internal cavity 73 and engage with the recesses 40 a and40 b on the extension arms 30 a and 30 b to releasably couple the guidecap 71 to the extension guide 18. The recesses 40 a and 40 b eachinclude an open vertical slot 82 connected to one end of a horizontalslot 84, and a closed vertical slot 86 connected to the opposite end ofthe horizontal slot. To attach the guide cap 71, the projections 80 arealigned with the open vertical slots 82 and pressure is applied to theguide cap 71 such that the cap advances onto the extension guide 18.When the projections 80 reach the bottom of the open vertical slot 82the cap is rotated until the projections 80 reach the end of thehorizontal slot 84. Pressure is then released from the guide cap 71 anda spring 88 working against proximal tabs 41 a, 41 b of the extensionarms draws the projections 80 into the closed vertical slots 86, therebysecuring the guide cap 71 to the extension guide 18.

The reduction capabilities of the extension guide 18 are enhanced withthe use of the guide cap 71. By way of example, the integral reductionfeatures described above are less effective when the extension arms 40 aand 40 b are flexible and allowed to splay. The guide cap 71 negatesthis challenge such that the surgeon is not required to choose betweeneasier rod insertion or better reduction. In addition, the body 72 ofthe guide cap 71 is adapted to releasably mate with independentreduction instruments should such an instrument be desired over theintegral reduction features of the extension guide 18. One example ofsuch an independent reduction instrument is depicted in FIG. 15 .

The reduction instrument 92 includes a connector 96 that releasablycouples the reduction instrument to the extension guide (via guide cap71). ‘The connector 96 has a receptacle 100 into which the proximal end78 of the guide cap 71 is received. The proximal end 78 is keyed to thereceptacle 100 so as to prevent rotation of the guide cap 71 andattached extension guide 18 relative to reduction instrument 92. Springclips 102 on the connector engage a groove 90 situated below theproximal end 78 to prevent translation of the guide cap 71 and attachedextension guide 18 relative to the reduction instrument 92. The springclips 102 have a tapered distal edge that extends into the receptacle100. The tapered edge allows the proximal end 78 to push past the springclips 102 until the tapered edge returns to rest in groove 90. Torelease the connection between the reduction instrument 92 and the guidecap 71 the proximal ends of the spring clips can be depressed and theconnector 96 lifted off the proximal end 78. In use, the reduction shaft94 is inserted through the guide cap 71 into extension guide 18 untilthe proximal end 78 of the guide cap 71 is locked into the receptacle100, as illustrated in FIGS. 16-17 . A reduction handle 104 may then beoperated to translate the reduction shaft 94 distally relative to theextension guide 18 to drive the rod 50 through the guide channel 40until the rod is fully seated in the housing 16. A locking cap driver105 may then be operated to advance the locking cap 51 into the housing16 and lock the rod 50 in place.

Having described the various features of the fixation anchor 10 andassociated instruments, an example method for the minimally invasiveimplantation of a spinal fixation construct will now be described.First, a spinal fixation anchor is anchored through the pedicle of eachvertebra to be fixated (e.g. three vertebra as shown in FIG. 17 ). Atleast one of the spinal fixation anchors is the spinal fixation anchor10. The remaining fixation anchors may also be the fixation anchor 10(as in FIG. 17 ). Alternatively, the remaining fixation anchors may beanchors adapted for use with independent guide structures thatreleasably couple to the anchors, as are generally known in the art.

With the fixation anchors 10 in position, a rod 50 appropriately sizedto span the distance between the end anchors is selected. At this point,the proximal joints 36 on one or more of the fixation anchors 10 may bebroken if the surgeon chooses to do so. By way of example, the surgeonmay choose to break the proximal joints 36 of the fixation anchor 10 atthe opposite end of the construct from which rod insertion will bedirected. During some insertion techniques the rod is inserted into theguide channel of the first fixation anchor 10 generally parallel to theextension guide while the insertion instrument is angled back towardsthe remainder of the extension guides 18. As the inserter is rockedtowards the insertion end, the rod advances through each guide. Severingthe proximal joints 36 on the extension guide 18 at the opposite end ofthe construct from rod insertion allows the inserter to advance betweenthe extension arms 30 a, 30 b of the end anchor (instead of having towork the inserter around the outside of the guide extension 18). Thissimplifies passage of the rod by facilitating proper alignment of therod during insertion. If the surgeon chooses to break the proximaljoints 36, the cam 64 and cylinder 56 of the breaking tool 44 arealigned and inserted into the extension guide 18 until the cap 54 restson the proximal end of the extension guide 18. The cam 64 is thenrotated with one hand while the counter torque handle 52 is held in theother hand until the proximal joints 36 break apart. The rod 50 is theninserted through the guide channels 40.

If necessary, (for example, if the rod 50 does not fully seat within theanchor housing 16 as would be the case if or more of the vertebrae arenot vertically aligned) one or more of the reduction methods describedabove may be employed to reduce the rod 50. If the rod 50 is seated lowenough in the guide channel 40 that the guide and advancement features42 are accessible above the rod then reduction may be accomplished byengaging a locking cap 51 with the guide and advancement features 42 andadvancing the locking cap 51 until the rod 50 and locking cap 51 arefully seated in the housing 16. If this reduction is to be carried outon a fixation anchor 10 whose proximal joints 36 had been previouslybroken, the guide cap 71 should preferably be coupled to the extensionguide 18 prior to reduction. Alternatively, if the rod 50 sits above theguide and advancement features 42 or the surgeon simply prefers toutilize an independent reduction tool, the guide cap 71 should beattached to the appropriate fixation anchor 10 whether or not theproximal joints 36 of that anchor have been broken. ‘The independentreduction instrument 92 is then coupled to the extension guide 18 andoperated to reduce the rod 50 into the housing 16 and a locking cap 51is engaged to lock the rod 50 in place. The surgeon may choose toutilize both the integral reduction features for reduction at onefixation anchor 10 and the independent reduction instrument forreduction at another of the fixation anchors 10. Reduction (whennecessary) and locking cap engagement is completed for each spinalfixation anchor in the construct.

With the rod 50 locked down along the entire construct the extensionguide 18 should be removed. First, any guide caps 71 utilized during theprocedure should be removed. Then the breaking tool 44 is used to breakthe proximal joints 36 of all extension guides 18 whose proximal joints36 remain intact. Finally, the extension arms 30 a and 30 b of eachspinal anchor 10 are removed by breaking the distal joints 40 a and 40b, respectively. According to an alternative sequence, the extensionguide 18 can be removed from each fixation anchor 10 in sequence as therod 50 is locked to each anchor 10. Once the extension guides 18 areremoved from each anchor 12, the final fixation construct is complete,as illustrated in FIG. 18 . and the incision(s) can be closed.

FIGS. 19 and 20 illustrate a spinal fixation system 110 configured forintroducing and building a posterior spinal fixation construct such asthat described above, according to one example embodiment. According toone example, the spinal fixation system 110 includes a pedicle screw112, an elongated spinal rod 114, and a guide assembly 116. Pediclescrews 112 are inserted bilaterally or unilaterally into multiplevertebra across one or more levels. In addition, fixation anchor 10 canbe utilized in place of pedicle screw 112 in one or more vertebra. Thespinal fixation system 110 may further include any of a variety ofinstruments configured to perform the installation and assembly of thespinal fixation construct including by way of example a reductioninstrument 117 shown in FIGS. 19 and 20 , as well as rod inserters,compression instruments, lock screw inserters, guide adjusters, tapguides, and dilators, of which various embodiments are described infurther detail below.

FIGS. 21-27 illustrate one example of a guide assembly 116 for minimallyinvasive implantation of the pedicle screw 112 and for guiding thespinal rod 114 into position. By way of example only, the guide assembly116 includes an outer sleeve 118 and a pair of inner arm members 120positioned within the outer sleeve 118. The arm members 120 areconfigured to releasably engage the housing 172 of the pedicle screw112. The arm members 120 are moveable between a first position and asecond position. When in the first “unlocked” position, the arm members120 are not engaged with in the pedicle screw 112. In the second,“locked” position, the arm members 120 are engaged with the pediclescrew 112, and the pedicle screw 112 is “locked” to the guide assembly116.

The outer sleeve 118 is a generally tubular member having a proximal end122, a distal end 124, and a lumen 126 extending longitudinally throughthe outer sleeve 118. The proximal end 124 includes a cap 128 that isconfigured to engage the inner arm members 120 (on the inside of the cap128) and a reduction instrument 117 (on the outside of the cap 128). Acircumferential groove 130 is positioned near the proximal end 122 andconfigured to receive the ridges 346 of the spring lock 344 of thereduction instrument 117. In this fashion, the guide assembly 116 may bereleasably coupled to the reduction instrument 117. The outer sleeve 118further includes a cylindrical recess 132 formed distally of thecircumferential groove 130 but in the proximal half of the outer sleeve118. The cylindrical recess 132 is configured to receive an actuator 134and is further configured to allow translation of the actuator 134 in aproximal/distal direction within the cylindrical recess 132. The outersleeve 118 further includes a pair of longitudinal slots 136 extendingproximally from the distal end 124 of the outer sleeve 118. Thelongitudinal slots 136 act in concert for form a channel 149 to guidethe spinal rod 114 to the surgical target site during implantation ofthe surgical fixation construct. By way of example only, the slots 136extend a little over halfway along the outer sleeve 118. The slots 136effectively divide the distal portion of the outer sleeve 118 into firstand second outer arms 138. The distal end of the outer arms 138 eachincludes a distal extension 140. The distal extension 140 is anextension of the outer sleeve 118 however it is narrower in width thanthe outer sleeve 118. A ridge 142 dimensioned to engage the housing 172of the pedicle screw 112 is positioned on the interior surface of thedistal extension 140. The ridge 142 is configured to engage theattachment groove 182 of the housing 172 to releasably lock the guideassembly 116 to the pedicle screw 112. The ridge 142 includes a taperedsurface 144 that enables the ridge 142 to slide over the top of thehousing 172 of the pedicle screw 112 during the engagement process. Theouter sleeve 118 is further provided with a plurality of elongatedapertures 146 positioned opposite one another on either side of theouter sleeve 118 and configured to receive protrusions 154 of the innerarm members 120 to facilitate the secure engagement of the inner arms120 to the outer sleeve 118.

The arm members 120 are each comprised of an elongatedpartially-cylindrical member having a proximal end 148 and a distal end150. The proximal ends 148 of the arm members 120 are dimensioned to bereceived within the cap 128 of the outer sleeve 118. The arm members 120each include a proximal protrusion 152 extending laterally from theouter surface of the arm member 120 and dimensioned to extend through acorresponding slot 146 positioned within the cylindrical recess 132 ofthe outer sleeve 118 and fixedly engage the actuator 134. In thisfashion, translation of the actuator 134 causes translation the firstand second arm members 120. Additional protrusions 156 are positionedalong the arm members 120 such that they are aligned with and receivedwithin corresponding slots 146 in the outer sleeve 118. The distal ends150 of the members 120 are configured to securely receive the top of thehousing 172 of the pedicle screw 112. To facilitate this secureengagement, the distal ends 150 of the arm members 120 include aplurality of prongs 158 configured to extend vertically along the sidesof the housing 172 upon engagement, as will be explained in furtherdetail below. Additionally, a raised protrusion 160 is provided betweenthe prongs 158 to engage a recess 184 in the top of the pedicle screw112. The prongs 158 and raised protrusion 160 act in concert to preventrotation of the housing 172 of the pedicle screw 112 during implantationof the spinal fixation construct.

The actuator 134 is positioned on the outside of the outer sleeve 118and is fixedly attached to the inner arms 120. As stated previously,translation of the actuator 134 causes translation the inner arms 120. Aspring 162 is provided that exerts a force distally the actuator and theinner arms 120 in order to bias the actuator 134 and inner arms 120 in a“locked” position. A stopper 164 is provided within the cap 132 toprovide a distal stop for the spring 162 and the inner arms 120. Theinner arms 120 may optionally be provided with a plurality of smallerapertures 166 to aid in the sterilization process.

The pedicle screw 112 includes a bone anchor 168 (e.g. shank with threadfeature 170) suitable for stable fixation to vertebral bone and ahousing 172 for capturing and locking a spinal rod 114. The housing 172has a base 174 that mates with the bone anchor 168 and a pair ofupstanding arms 176 separated by a rod channel 178. The arms 176 areequipped with a locking cap guide and advancement feature 180, such asby way of example, a helically wound flange feature disposed on theinterior face of each arm 176. The locking cap guide and advancementfeature 180 mates with a complementary guide and advancement feature ona lock screw (not shown, but similar to the lock screw 119 shown anddescribed in relation to FIGS. 69-74 ). The lock screw 119 engages theupstanding arms 176 via the complementary guide and advancement features180,376 to press and lock the fixation rod 114 into the housing 172.

The housing 172 and anchor 168 may be mated with a polyaxial engagementsuch that the housing 172 can pivot relative to the anchor 168 in anydirection. The engagement may also be such that the pivoting movementmay be inhibited in one or more directions. By way of example, thehousing 172 and anchor 168 may be mated with a uniplanar engagement suchthat the housing pivots relative to the anchor 168 in a single plane.The housing 172 and anchor 168 may also be fixed such that no movementis possible between the housing 172 and anchor 168.

The housing 172 further includes a pair of attachment grooves 182, oneattachment groove 182 formed in each of the upstanding arms 176. Theattachment grooves are dimensioned to receive the ridges 142 on theouter sleeve 118 of the guide assembly 116 to releasably lock the guideassembly 116 to the pedicle screw 112. The top of each arm 176 furtherincludes a recess 184 formed therein. The recesses 184 have acorresponding shape and are dimensioned to receive the raisedprotrusions 160 on the distal end of the inner arm members 120 of theguide assembly 116. This interaction helps to prevent rotation of thehousing 172 of the pedicle screw 112 during implantation of the spinalfixation construct.

FIGS. 32-34 illustrate the guide assembly 116 engaged to a pedicle screw112. In order to accomplish this, once the pedicle screw 112 has beenseated in the appropriate position in the surgical target site, theguide assembly 116 is advanced distally along the operative corridoruntil the distal end of the outer sleeve 118 contacts the housing 172 ofthe pedicle screw 112. The guide assembly 116 is then further advancedsuch that the ridges 142 snap into the attachment grooves 182 on thehousing 172. At this point the outer sleeve 118 is secured to thepedicle screw 112. The actuator 134 is then advanced in a distaldirection, which causes the simultaneous distal advancement of the innerarms 120 of the guide assembly 116. The inner arms 120 are advanced suchthat and until each pair of prongs 158 are positioned on either side ofthe upstanding arms 176 of the housing 172 and the raised protrusions160 are seated within recesses 184 on the housing 172. At this point theinner arms 120 are secured to the pedicle screw 112 and the housing 172is prevented from rotation relative to the guide assembly 116. Uponcoupling of the guide assembly 116 and the pedicle screw 112, theopposed guide slots 168 formed between the outer arms 138 of the outersleeve 118 of the guide assembly 116 align with the rod channel 178 ofthe housing 172 to define an enclosed guide channel 186 that isdimensioned to allow passage of a fixation rod 114. Utilizing the guidechannel 186 to align the rod 114 with the housing rod channel 178reduces the need for fiddlesome manipulation of the housing 172 and/orrod 114 near the surgical target site, as well as the associated need tofully visualize the pedicle screw 112 and/or the housing 172 during rodinsertion. Thus, the overall size of the incision required to implant afixation construct using the described fixation system 110 issignificantly reduced compared to open procedures. Once the rod 114 hasbeen seated in the housing 172 and secured with a lock screw 119 (asdescribed below), the guide assembly 116 may be removed from theoperative corridor. To accomplish this, a proximal force is applied tothe actuator 134, which will disengage the inner arms 120 from thehousing 172. The outer sleeve 118 may be disengaged from the housing 172by applying an appropriate amount of proximal force on the guideassembly 116. Once both the outer sleeve 118 and the inner arms 120 havebeen disengaged from the housing 172, the guide assembly 116 may beremoved from the operative corridor.

FIGS. 35-37 illustrate an example of a guide assembly 188 according toan alternative embodiment of the present invention for use with thespinal fixation system 110 described above.

The guide assembly 188 is substantially similar to the guide assembly116 described above, such that repeat description of like parts isunnecessary. By way of example only, the guide assembly 188 includes anouter sleeve 190 and a pair of inner arm members 192 positioned withinthe outer sleeve 190. The arm members 192 are configured to releasablyengage the housing 208 of the pedicle screw 206 (FIGS. 38-39 ). The armmembers 192 are moveable between a first position and a second position.When in the first “unlocked” position, the arm members 192 are notengaged with in the pedicle screw 206. In the second, “locked” position,the arm members 192 are engaged, with the pedicle screw 206, and thepedicle screw 206 is “locked” to the guide assembly 116. As with theguide assembly 116, the guide assembly 188 includes an actuator 194 thatfacilitates the movement of the arm members 192 from the first to thesecond position.

The guide assembly 188 is substantially identical to the guide assembly116 with the exception of two features that will be discussed in detailbelow. It is to be understood that any or all of other featuresdescribed in conjunction with the guide assembly 116 may be present withrespect to the guide assembly 188 in both structure and function.Therefore, repeat description of common features is not necessary. Inaddition to many of the features described in conjunction with the guideassembly 116, the guide assembly 188 includes a castle nut 196protruding from the top of the outer sleeve 190. The castle nut 196interacts with the actuator 194 and serves as a visual indicator ofwhether the guide assembly 188 is locked to the pedicle screw 206. Morespecifically, when the inner arm members 192 are in the first,“unlocked” position, the castle nut 196 protrudes from the top of theouter sleeve 190 (FIG. 35 ). When the inner arm members 192 are in thesecond position, the castle nut can be advanced (blocking return of theinner arm members), making the second position the “locked” position asthe guides cannot be disengaged from the pedicle screw 206. The guide is“locked”, when the castle nut 196 sits flush the top of the outer sleeve190 (FIG. 36 ) and thus serves as a visual indication as to whether theguide assembly 188 is locked to the pedicle screw 206.

Referring to FIG. 37 , the second major difference between the guideassembly 188 and the guide assembly 116 is in the distal engagement ends198 of the inner arm members 192. The distal ends 198 of the arm members192 are configured to securely receive the top of the housing 208 of thepedicle screw 206. To facilitate this secure engagement the distal ends198 of the arm members 192 include a plurality of prongs 200 configuredto extend vertically along the sides of the housing 208 upon engagement.The prongs 200 differ from the prongs 158 in that each prong 200includes an additional cutout area 202 on a pedicle screw engagementsurface that interacts with the pedicle screw 206 to provide a moresecure engagement, as will be described below. As with the first exampledescribed above, a raised protrusion 204 is provided between the prongs200 to engage a recess 220 in the top of the pedicle screw 206. Theprongs 200 and raised protrusion 204 act in concert to prevent rotationof the housing 208 of the pedicle screw 206 during implantation of thespinal fixation construct.

FIGS. 38-39 illustrate a pedicle screw 206 configured for use with theguide assembly 188 according to an alternative example. The pediclescrew 206 is similar to the pedicle screw 112 described above in that itincludes a bone anchor (e.g. shank with thread feature—not shown)suitable for stable fixation to vertebral bone and a housing 208 forcapturing and locking a spinal rod 114. The bone anchor portion of thepedicle screw 206 is identical to the bone anchor portion of pediclescrew 112 described above. The housing 208 has a base 210 that mateswith the bone anchor and a pair of upstanding arms 212 separated by arod channel 214. The arms 212 are equipped with a locking cap guide andadvancement feature 216, such as by way of example, a helically woundflange feature disposed on the interior face of each arm 212. Thelocking cap guide and advancement feature 216 mates with a complementaryguide and advancement feature on a lock screw (not shown, but similar tothe lock screw 119 shown and described in relation to FIGS. 69-74 ). Thelock screw engages the upstanding arms 212 via the complementary guideand advancement features 216, 376 to press and lock the fixation rod 114into the housing 208.

The housing 208 further includes a pair of attachment grooves 218, oneattachment groove 218 formed in each of the upstanding arms 212. Theattachment grooves 218 are dimensioned to receive the ridges 195 (FIG.35 ) on the outer sleeve 190 of the guide assembly 188 to releasablylock the guide assembly 188 to the pedicle screw 206. The top of eacharm 212 further includes a recess 220 formed therein. The recesses 220have a corresponding shape and are dimensioned to receive the raisedprotrusions 204 on the distal end of the inner arm members 192 of theguide assembly 188. This interaction helps to prevent rotation of thehousing 208 of the pedicle screw 206 during implantation of the spinalfixation construct The housing 208 also includes a plurality of verticalcutouts 222 formed in each upstanding arm 212 on either side of the rodchannel 214. The vertical cutouts 222 interact with the prongs 200 ofthe inner arm members 192 to provide a more secure engagement betweenthe guide assembly 188 and the pedicle screw 206. More specifically, thecutout areas 202 of the prongs 200 are complimentary in shape to thevertical cutouts 222 on the arms 212 such that upon engagement, eachprong 200 will contact at least three distinct surfaces of thecorresponding upstanding arm 212. FIGS. 40-41 illustrate the guideassembly 188 engaged to the housing 208 of a pedicle screw 206.

FIGS. 42-44 illustrate an example of a guide assembly 224 according to athird example embodiment of the present invention for use with thespinal fixation system 110 described above. The guide assembly 224 issubstantially similar to the guide assemblies 116, 188 described above,such that repeat description of like parts is unnecessary. It is to beunderstood that any or all of other features described in conjunctionwith the guide assemblies 116, 188 may be present with respect to theguide assembly 224 in both structure and function. By way of exampleonly, the guide assembly 224 includes an outer sleeve 226 and a pair ofindependent inner arm members 228 positioned within the outer sleeve224. The arm members 228 are configured to releasably engage the housing228 of the pedicle screw 206 (FIGS. 38-39 ). The distal engagementregion of the arm members 228 and the interaction with the pedicle screw206 is identical to that described in relation to the guide assembly188. As with the previously described examples, the arm members 228 aremoveable between a first position and a second position. When in thefirst “unlocked” position, the arm members 228 are not engaged with inthe pedicle screw 206. In the second, “locked” position, the arm members228 are engaged with the pedicle screw 206, and the pedicle screw 206 is“locked” to the guide assembly 224. Unlike the guide assemblies 116,188, however, the guide assembly 224 does not include the same actuatorto facilitate the movement of the arm members 228 from the first to thesecond position. As will be described below, the guide assembly 224instead has a castle nut 230 that acts as the actuator. The castle nut230 attaches directly to the arm members 228, and controls theadvancement (and retreat) of the arms.

In addition to many of the features described in conjunction with theguide assemblies 116, 188, the guide assembly 224 includes a castle nut230 protruding from the top of the outer sleeve 226. As with the guideassembly 188, the castle nut 230 serves as a visual indicator of whetherthe guide assembly 224 is locked to the pedicle screw 206. Morespecifically, when the inner arm members 228 are in the first,“unlocked” position, the castle nut 230 protrudes from the top of theouter sleeve 226. When the inner arm members 228 are in the second,“locked” position and engaged to a pedicle screw 206, the castle nut 230is flush with the guide and consequently not visible above the top ofthe outer sleeve 226 (FIG. 42 ).

Unlike the guide assembly 188 described, the castle nut 230 not onlylocks the position of the inner arms after the arms move into position,the castle nut 230 also acts as the actuator to control the translationof the inner arms 228. To do this the inner arms 228 are attacheddirectly to the castle nut 230. The proximal ends 232 of the inner arms228 include a groove 234 that is dimensioned to engage a correspondingridge 236 in the interior of the castle nut 230. Alternatively, theproximal ends 232 of the inner arms 228 may be provided with ridges thatare received within corresponding grooves formed in the interior of thecastle nut (not shown). Any combination of grooves and ridges may beemployed to mate the inner arms 228 with the castle nut 230. In anycase, by way of example only, the inner arms 228 may be mated with thecastle nut 230 via a ridge/groove interaction. A tool (not shown) may beattached to the castle nut 230 (for example via slot 238) to help rotatethe nut and lock or unlock the inner arms 228 and pedicle screw 206. Thegroove/ridge interaction between the castle nut 230 and the inner arms228 ensure that the castle nut 230 is able to rotate freely relative tothe inner arms 228 while still controlling translation. The guideassembly 224 may be provided with guide slots 240 that extendsubstantially the length of the outer sleeve 226. Relative to guideassemblies 116, 188, the longer guide slots 240 on the guide assembly224 are possible due to the absence of an actuator to controltranslation of the inner arms 228.

FIGS. 45-52 illustrate several examples of spinal rods 114, 114 aconfigured for use with the surgical fixation system described herein.By way of example, the spinal rod 114, 114 a may be provided in anylength corresponding to the number of spinal levels to be fixed. Thespinal rods 114, 114 a are generally cylindrical elongated rods. Thespinal rods 114, 114 a may be straight or curved. By way of exampleonly, the spinal rods 114, 114 a have a first end 242, 242 a that isgenerally rounded and a second end 244, 244 a that is configured toengage a rod inserter such as the rod inserter 250 shown and describedbelow in relation to FIG. 53 . The second end 244, 244 a includes a post246, 246 a having a shape corresponding to the shape of the rod cavity266 on the rod inserter 250. By way of example only, the spinal rod 114includes a post 246 having a generally octagonal cross-sectionalfootprint. Post 246 a is similar but is wider and has a rounded edge.The post 246, 246 a also includes a recess 248, 248 a formed on an uppersurface of the post 246, 246 a and configured to receive the distal lip278 of the locking element 268 on the rod inserter 250. The recess 248,248 a and distal lip 278 cooperate to temporarily secure the rod 114,114 a to the rod inserter 250.

FIGS. 53-58 illustrate a first example of a rod inserter 250 configuredfor use with the spinal fixation system 110 according to one embodimentof the present invention. By way of example only, the rod inserter 250is an adjustable-angle rod inserter that introduces the spinal rod 114through the operative corridor at one angle (relative to the inserter),and then pivots the rod at the surgical target site. This enables longerspinal rods 114 to be inserted through an operative corridor, and italso allows for smaller incisions because less room is needed to insertthe spinal rod.

By way of example only, the rod inserter 250 includes an outer sleeve252, an inner shaft 254, a handle 256, and a rod holder 258. The outersleeve 252 is an elongated cylindrical member having an inner lumenextending throughout. The inner shaft 254 is an elongated rod memberhaving a knob 260 at the proximal end and an engagement post 262 at thedistal end. The knob 260 is configured for handling by a user, andallows to user to pull up (proximally) on the knob to disengage the post262 from the first and/or second shaft recesses 270, 274. The knob 260can also be rotated in a clockwise or counterclockwise direction inorder to lock or unlock the setscrew 272, as will be described below.The engagement post 262 is configured to engage the first and secondshaft recesses 270, 274 to maintain the rod inserter 250 in either thefirst or second position. A spring 264 is located within the handle 256and acts to bias the inner shaft 254 in a distal direction. This ensuresthat the rod inserter 250 is secured in either the first or secondpositions, and a positive action is required by the user to effect achange in position.

The rod holder 258 is pivotably attached to the distal end of the outersleeve 252, and is configured to be pivoted from a first position to asecond position and then back to the first position. The rod holder 258includes a rod cavity 266, a locking element 268, first shaft recess270, a setscrew 272, and second shaft recess 274. The rod cavity 266 isconfigured to receive the post 246 of the spinal rod 114. The lockingelement 268 is positioned within the rod holder 258 and is moveable froma first unlocked position to a second locked position. The lockingelement 268 includes a proximal recess 276, a distal lip 278, and acentral cavity 280. The proximal recess 276 is configured to receive thesetscrew 272, and is firmly attached to the setscrew via a snap ring282. The snap ring allows the setscrew 272 to rotate within the proximalrecess 276 while being advanced or retreated by the inner shaft 254, andalso ensures that the locking element 268 is advanced and/or retreatedalong with the setscrew 272. A lockstop 284 in the form of a pin (by wayof example only) extending through the cavity prevents the lockingelement 268 (and setscrew 272) from being retreated so much that itbecomes disengaged entirely from the rod holder 258. The distal lip 278is configured to be seated within the recess 248 of the spinal rod 114such that when the rod inserter is in the locked position, the spinalrod 114 is secured within the rod cavity 266 and will not becomedislodged therefrom. The setscrew 272 is positioned within the firstshaft recess 270, The second shaft recess 274 is configured to receiveengagement post 262 when the rod holder 250 is in the second position.This interaction temporarily locks the rod holder 250 in the secondposition.

In use, the rod inserter 250 is initially provided in a first position(FIG. 53 ) without the spinal rod 114 and the rod holder 258 in anunlocked position. In this first position, the first shaft recess 270(and consequently the setscrew 272) is in alignment with the centrallumen of the outer shaft 252, The spinal rod 114 is then mated with therod holder 258 by inserting the post 246 into the rod cavity 266 suchthat the recess 248 is facing the locking element 268. The knob 260 isrotated in a clockwise direction, which advances the setscrew 272 andlocking element 268 in a distal direction until the distal lip 278 ofthe locking element 268 is seated within the recess 248. At this pointthe spinal rod 114 is secured to the rod inserter 250. The user thenexerts a proximal force on the knob 260 causing the inner shaft 254 tomove in a proximal direction and further causing the engagement post 262to become disengaged from the first shaft recess 270. The rod holder 258will then pivot (due to the pull of gravity on the spinal rod 114) suchthat the second shaft recess 274 becomes aligned with the outer shaft252. The user may then release the knob 260, which due to the spring 264advances the inner shaft 254 distally and causes the engagement post 262to be received within the second shaft recess 274. The rod holder 258 isnow secured in the second position (FIG. 54 ). In the second position,the spinal rod 114 is positioned at an obtuse angle relative to the rodinserter 250, which reduces the size of the operative corridor requiredto advance the rod. The rod 114 may be advanced through the operativecorridor using a guide assembly such as the guide assembly 116 (or anyof the other examples) described above.

As the distal tip of the rod reaches the target site it may becomenecessary to pivot the rod to further its advancement. This may beaccomplished by once again applying a proximal force on the knob 260 torelease the engagement post 262 from the second shaft recess 274, Thisallows the rod holder 258 to pivot toward the first position. Once therod 114 is fully inserted, the user may release the knob 260 to reengagethe engagement post 262 and the first shaft recess 270. The rod holder258 is once again in the first position (FIG. 55 ). Once the rod 114 isseated within the pedicle screw 112 and secured as described above (andbelow), the rod 114 is ready to be detached from the rod inserter 250.To accomplish this, it is necessary to return the rod holder 258 to thefirst position (as just described) if it has not already been doneduring insertion of the rod. With the rod holder 258 in the firstposition, the knob 260 is turned counterclockwise to translate thesetscrew 272 (and locking element 268) in a distal direction, whichremoves the distal lip 278 from the recess 248 and unlocks the rod 114.The rod inserter 250 may then be safely removed from the surgical targetsite through the operative corridor.

FIGS. 59-61 illustrate a second example of a rod inserter 290 configuredfor use with the spinal fixation system 110 according to anotherembodiment of the present invention, By way of example only, the rodinserter 290 is a fixed-angle rod inserter that introduces the spinalrod 114 through the operative corridor at one angle (relative to theinserter).

By way of example only, the rod inserter 290 includes a housing tube292, a center screw 294, a handle 296, and a rod holder 298. The housingtube 292 is an elongated cylindrical member having an inner lumenextending throughout. The center screw 294 is an elongated rod memberhaving a driver engagement recess 300 at the proximal end and anengagement post 302 at the distal end. The driver engagement recess 300is configured to receive an engagement end of a suitable driverinstrument (not shown). The center screw 294 can be rotated in aclockwise or counterclockwise direction in order to lock or unlock thespinal rod 114 to the rod inserter 290, as will be described below. Theengagement post 302 is configured to engage the locking element 306. Aspring (not shown) is located within the housing tube 292 and acts tobias the locking element 306 in an unlocked position.

The rod holder 298 is formed in the distal end of the housing tube 292.‘The rod holder 298 includes a rod cavity 304 and a locking element 306.The rod cavity 304 is configured to receive the post 246 of the spinalrod 114. ‘The locking element 306 is positioned within the rod holder298 and is moveable from a first unlocked position to a second lockedposition. The locking element 298 includes a proximal recess 308 and adistal lip 310. The proximal recess 308 is configured to receive theengagement post 302. The distal lip 310 is configured to be seatedwithin the recess 248 of the spinal rod 114 such that when the rodinserter 290 is in the locked position, the spinal rod 114 is securedwithin the rod cavity 266 and will not become dislodged therefrom.

In use, the rod inserter 290 is initially provided without the spinalrod 114 and the rod holder 298 in an unlocked position. The spinal rod114 is then mated with the rod holder 298 by inserting the post 246 intothe rod cavity 304 such that the recess 248 is facing the lockingelement 306. The center screw 294 is rotated in a clockwise direction,which advances the locking element 306 in a distal direction until thedistal lip 310 of the locking element 306 is seated within the recess248. At this point the spinal rod 114 is secured to the rod inserter290. The rod 114 may be advanced through the operative corridor using aguide assembly such as the guide assembly 116 (or any of the otherexamples) described above. Once the rod 114 is seated within the pediclescrew 112 and secured as described above (and below), the rod 114 isready to be detached from the rod inserter 290. To accomplish this, thecenter screw 294 is turned counterclockwise to translate the lockingelement 306 in a distal direction, which removes the distal lip 310 fromthe recess 248 and unlocks the rod 114. The rod inserter 290 may then besafely removed from the surgical target site through the operativecorridor.

FIGS. 62-63 illustrate a third example of a rod inserter 312 configuredfor use with the spinal fixation system 110 according to anotherembodiment of the present invention. By way of example only, the rodinserter 312 is a mostly fixed-angle rod inserter that capable of slightvariation in the introduction angle that introduces the spinal rod 114through the operative corridor at one angle (relative to the inserter),and then allows for a slight adjustment in the angle (for example ±15°)for easier final seating of the rod 114 within the pedicle screw 112.

By way of example only, the rod inserter 312 includes a handle 314, ahousing tube 316. a rod holder 318, an attached driver 320, and a balllinkage 322. The housing tube 316 is an elongated cylindrical memberhaving an inner lumen extending throughout. The housing tube 316 may becurved so that the handle 314 is oriented at an angle (as opposed tolinear) relative to the operative corridor. This allows for improvedvisualization of the surgical target site by the surgeon as the rod isbeing inserted. The rod holder 318 is formed in the distal end of thehousing tube 316. The rod holder 318 includes a rod cavity 324 and alocking element 326. The rod cavity 324 is configured to receive thepost 246 of the spinal rod 114. The locking element 326 is positionedpartially within the rod holder 318 and partially within the inner lumenof the housing tube 316 and is moveable from a first unlocked positionto a second locked position. The locking element 326 includes a proximalrecess 328, a spring element 330, and a distal lip 332. The proximalrecess 328 is configured to receive the distal end of the ball linkage322. The spring element 330 helps to bias the locking element 326 in adistal direction. The distal lip 332 is configured to be seated withinthe recess 248 of the spinal rod 114 such that when the rod inserter 312is in the locked position, the spinal rod 114 is secured within the rodcavity 324 and will not become dislodged therefrom.

The rod inserter 312 includes an attached driver 320 at the proximal endof the handle 314. The driver 320 includes a drive shaft 334, a driverhandle 336, and a push button 338. The drive shaft 334 is partiallythreaded (and interacts with a partially threaded lumen inside thehandle 314) such that rotating the driver handle 336 in a clockwisedirection advances the drive shaft 334 in a distal direction, androtating the driver handle 336 in a counterclockwise direction retreatsthe drive shaft 334 in a proximal direction. The distal end of the driveshaft 334 abuts with the ball linkage 322, and thus distal advancementof the drive shaft 334 causes distal advancement of the ball linkage322. The ball linkage is a series of spheres abutting one another thatextend between the distal end of the drive shaft 334 and the proximalrecess 328 of the locking element 326. Further advancement of the driveshaft 334 will then cause the locking element 326 to engage the spinalrod 112 and lock it within the rod holder 318. Thus, the ball linkage322 enables direct control of the locking element 326 even though thehousing tube 316 is curved. The push button 338 provides an internalstop which allows the user to loosen the rod slightly (while stillretaining the rod) which allows for a slight adjustment in the angle(for example ±15°) for easier final seating of the rod 114 within thepedicle screw 112.

In use, the rod inserter 312 is initially provided without the spinalrod 114 and the rod holder 318 in an unlocked position. The spinal rod114 is then mated with the rod holder 318 by inserting the post 246 intothe rod cavity 324 such that the recess 248 is facing the lockingelement 326. The driver handle 336 is rotated in a clockwise direction,which as described above advances the locking element 326 in a distaldirection until the distal lip 332 of the locking element 326 is seatedwithin the recess 248. At this point the spinal rod 114 is secured tothe rod inserter 312. The rod 114 may be advanced through the operativecorridor using a guide assembly such as the guide assembly 116 (or anyof the other examples) described above. During final seating of the rod114 within the pedicle screw 112, it may become desirable to have aslight variation of the angle of insertion. This may be accomplished bypressing the push button 338, which loosens the rod 114 slightly (whilestill retaining the rod) which allows for a slight adjustment in theangle (for example ±15°). Once the rod 114 is seated within the pediclescrew 112 and secured as described above (and below), the rod 114 isready to be detached from the rod inserter 312. To accomplish this, thedriver handle 336 is turned counterclockwise to translate the lockingelement 326 in a distal direction, which removes the distal lip 332 fromthe recess 248 and unlocks the rod 114. The rod inserter 312 may then besafely removed from the surgical target site through the operativecorridor.

FIGS. 64-70 illustrate a reduction instrument 117 according to oneexample embodiment of the spinal fixation system 110. Generally, thereduction instrument 117 is used to fully seat (“reduce”) the spinal rod114 into the pedicle screw 112 and thereafter insert a lock screw 119 tosecure the rod 114 to the screw 112. The reduction instrument 117 isconfigured for use with any of the guide assemblies described above(e.g. 18, 116, 188, 224), however for the purpose of illustration thereduction instrument 117 will be described in use with the guideassembly 116 shown and described in relation to FIG. 21 et seq. Thereduction instrument 117 includes a connector 340 that releasablycouples the reduction instrument 117 to the guide assembly 116 (via thecap 128). The connector 340 has a guide cavity 342 into which theproximal end 122 of the outer sleeve 118 (featuring the cap 128) isreceived. The proximal end 122 is keyed to the guide cavity 342 so as toprevent rotation of the guide assembly 116 relative to the reductioninstrument 117. Spring locks 344 on the connector 340 are provided toprevent translation of the guide cap 128 and attached guide assembly 116relative to the reduction instrument 117. Specifically, the spring locks344 include ridges 346 that extend through the connector 340 into theguide cavity 342 and engage the circumferential groove 130 situatedbelow the proximal end 122 when the guide assembly 116 is mated with thereduction tool 117. The ridges 346 allow the proximal end 122 of theguide assembly 116 to push past the spring locks 344 until the ridges346 snap into place within the circumferential groove 130. To releasethe connection between the reduction instrument 117 and the guideassembly 116, the proximal ends of the spring locks 344 can be depressedcausing the ridges 346 to lift out of the circumferential groove 130,thus allowing the removal of the connector 128 from the guide cavity342.

The reduction instrument 117 has an elongated central shaft 348extending longitudinally through the entire length of reductioninstrument 117. The reduction instrument 117 further includes a rotationhandle 352, a translation handle 354, a threaded shaft 358, a spring362, an inner sleeve 364, and an outer sleeve 366. The central shaft 348has a proximal portion 349, a distal portion 350, and a block portion351 that is situated between the proximal portion 349 and the distalportion 350. The proximal portion 349 is generally cylindrical andextends proximally from the block portion 351 through the threaded shaft358, translation handle 354, and rotation handle 352. The distal portion350 is generally cylindrical (with a greater diameter than the proximalportion 349) and extends distally from the block portion 351. Therotation handle 352 extends through the translation handle 354 and has aproximal knob 353 configured for manipulation by a user. The rotationhandle is fixedly attached to the central shaft 348, and thus rotationof the rotation handle causes rotation of the central shaft 348. Therotation handle 352 may be provided with band markers 355 spaced apartat a specific distance (e.g. 10 mm) to indicate the amount of reduction.The translation handle 354 has a threaded aperture 356 that isdimensioned to receive the proximal end of the threaded shaft 358. Thetranslation handle 354 is rotatable in both clockwise andcounterclockwise directions, As will be explained, turning thetranslation handle 354 in a clockwise direction ultimately advances thecentral shaft 348 and reduces the spinal rod 114 into the pedicle screw112. As will be explained, the rotation handle 352 rotates independentlyof the translation handle 354 in both a clockwise and counterclockwisedirection, and turning the rotation handle 352 in a clockwise directionadvances the lock screw 119 into the housing 172 of the pedicle screw112.

The threaded shaft 358 is mated at its proximal end with the threadedaperture 356 of the translation handle 354 and engages with the centralshaft 348 at the proximal side of the block portion 351. An abutmentinsert 357 is positioned proximally of the block portion 351 andprovides an abutment surface for the threaded shaft 358. Rotation of thetranslation handle 354 causes the threaded shaft 358 to translate up ordown through the threaded aperture 356, translating the central shaft348 and rotation handle 352 up or down with it. The distal portion 350of the central shaft 348 extends distally from the block portion 351.The distal portion 350 extends through a spring 362 and an inner sleeve364. The spring 362 is positioned just distally of the block portion351, between the block portion 351 and the inner sleeve 364. The spring362 and inner sleeve 364 are contained within an outer sleeve 366. Thedistal portion 350 of the central shaft 348 has a distal roundedreduction end 361 that is configured to engage the spinal rod 114 andreduce it into the housing 172. Alternatively, the distal reduction end361 may be a generally planar rather than rounded (for example, FIGS.71-74 illustrate a reduction instrument 117 with a generally planarreduction end 361 a). A snap ring 368 is positioned within a recess 370formed just proximally of the distal rounded reduction end 361. The snapring 368 is sized and configured to prohibit passage of the lock screw119 until the spinal rod 114 is fully reduced into the housing 172 andan appropriate distal force is applied to the lock screw 119 by theinner shaft (as will be explained below). A lock screw engagementfeature 363 is provided on the distal portion 350 just proximally of therecess 370. The lock screw engagement feature 363 is configured totemporarily hold a lock screw 119 while preventing rotation of the lockscrew 119 relative to the central shaft 348. By way of example only, thelock screw engagement feature 363 may have a hexalobe shape as shown inFIGS. 64 and 74 , however other shapes that prevent rotation of the lockscrew 119 relative to the central shaft 348 are possible. One or morewindows 372 may be formed in the outer sleeve 366 near the top of theinner sleeve 364, The windows 372 may provide a visual indication (forexample, a color coded indication) of when the rod 114 is fully reducedand the lock screw 119 is in position at the top of the housing 172awaiting engagement.

The lock screw 119 has a central aperture 374 configured to allowpassage of the distal portion 350 of the central shaft 348 therethrough.The central aperture 374 has a shape complimentary to the lock screwengagement feature 363 of the central shaft 348. By way of example only,that shape is hexalobe, however other shapes are possible. The lockscrew 119 also has a guide and advancement feature 376 such as by way ofexample, a helically wound flange feature disposed on the outercircumference of the lock screw 119. The guide and advancement feature376 mates with a complementary locking cap guide and advancement feature180 on the housing 172. The lock screw 119 engages the housing 172 viathe complementary guide and advancement features 180, 376 to press andlock the fixation rod 114 into the housing 172.

In use, once the pedicle screws 112 have been properly seated and a rod114 introduced, the reduction instrument 117 is engaged to a guideassembly 116 as previously described. At least one lock screw 119 isattached to the lock screw engagement feature 363 of the central shaft348. The translation handle 354 is operated in a clockwise direction toadvance the central shaft 348 in a distal direction such that the distalengagement end 361 contacts the spinal rod 114. At some point duringthis advancement, the lock screw 119 will come into contact with the topof the housing 172. However, because the central shaft 348 (and thus theset screw) is not rotating at this point, the set screw does not engagethe guide and advancement feature and advance into housing 172. However,the block portion 351 of the central shaft 348 continues to translatedistally, advancing the engagement end 361 through the central aperture374 of the lock screw 119 while the lock screw 119 remains stationaryatop the housing 172. The inner sleeve 364, which abuts the lock screw119 and extends proximally therefrom also remains stationary during thistime. Spring 362 allows this movement the of the engagement end 351relative to the lock screw 119. The spring 362, which is positionedbetween the block portion 351 and the inner sleeve 364, compresses dueto the transfer of translational energy from the block portion 351 tothe spring 362. This continues until the spinal rod 114 is fully reducedwithin the housing 172 of the pedicle screw 114, which may be indicatedwith a marker on the rotation handle (e.g. a green band near the top ofthe rotation handle that becomes hidden within the translation handlewhen the rod is fully reduced—not shown). For example, the rod 114 maybe fully reduced just before the rod bottoms out in the housing 172.This prevents excessive loads on the reducer from over reduction. Thoughnot shown, a stop may be provided to ensure reduction stops just priorto bottoming out. By way of example, the proximal end of the threadedshaft 358 may have a larger diameter than the threaded aperture 356 suchthat the proximal end can't pass out of the translation handle, therebystopping translation of the threaded shaft. At this point the lock screw119 is in position at top of the housing 172 of the pedicle screw 112,but the complementary guide and advancement features 180, 376 are notyet engaged. To do so, the rotation handle 352 may be briefly rotated ina clockwise or counterclockwise direction to align the guide andadvancement features on the lock screw 119 and housing 172. Though notnecessarily, an audible “click” may be heard, indicating that the guideand advancement features 180, 376 have initially mated and are ready forfull installation. The rotation handle 352 is then rotated in aclockwise direction. The engagement of the guide and advancementfeatures 180, 376 combined with the release of the energy contained inthe compressed spring push the lock screw 119 down the central shaft 348and into the housing 172. When the lock screw 119 is fully seated, therotation handle 354 will cease to rotate. To effect removal of thereduction instrument 117, the translation handle 354 is briefly turnedcounterclockwise (e.g. 10 mm) to back off reduction. The spring locks344 are disengaged as described above and the reduction instrument 117may be removed from the operative corridor.

FIGS. 75-77 illustrate a reduction instrument 380 according to anotherexample embodiment of the spinal fixation system 110. Generally, thereduction instrument 380 is used to fully seat (“reduce”) the spinal rod114 into the pedicle screw 112 and thereafter insert a lock screw 119 tosecure the rod 114 to the screw 112. The reduction instrument 380 isconfigured for use with any of the guide assemblies described above(e.g. 18, 116, 188, 224), however for the purpose of illustration thereduction instrument 380 will be described in use with the guideassembly 116 shown and described in relation to FIG. 21 et seq. Thereduction instrument 380 differs from the reduction instrument 117previously described in that the reduction instrument 380 uses a “pistolgrip” mechanism to cause translation of the central shaft 390 to reducethe rod 114. All other features are identical and it is to be understoodthat any feature previously described with respect to the reductioninstrument 117 may be provided on the reduction instrument 380 withoutdeparting from the scope of the present invention. The reductioninstrument 380 includes a connector 382 that releasably couples thereduction instrument 380 to the guide assembly 116 (via the cap 128).The connector 382 has a guide cavity 384 into which the proximal end 122of the outer sleeve 118 (featuring the cap 128) is received. Theproximal end 122 is keyed to the guide cavity 384 so as to preventrotation of the guide assembly 116 relative to the reduction instrument380. Spring locks 386 on the connector 382 are provided to preventtranslation of the guide cap 128 and attached guide assembly 116relative to the reduction instrument 380. Specifically, the spring locks386 include ridges 388 that extend through the connector 382 into theguide cavity 384 and engage the circumferential groove 130 situatedbelow the proximal end 122 when the guide assembly 116 is mated with thereduction tool 380. The ridges 388 allow the proximal end 122 of theguide assembly 116 to push past the spring locks 386 until the ridges388 snap into place within the circumferential groove 130. To releasethe connection between the reduction instrument 380 and the guideassembly 116, the proximal ends of the spring locks 386 can be depressedcausing the ridges 388 to lift out of the circumferential groove 130,thus allowing the removal of the connector 128 from the guide cavity384.

The reduction instrument 380 has an elongated central shaft 390extending longitudinally through the entire length of reductioninstrument 380. The reduction instrument 380 further includes a rotationhandle 392, a translation handle 394, a translation shaft 396, a spring(not pictured), an inner sleeve 398, and an outer sleeve 400. Thecentral shaft 390 has a proximal portion (not shown), a distal portion402, and a block portion 404 that is situated between the proximalportion and the distal portion 402. The proximal portion is generallycylindrical and extends proximally from the block portion 404 throughthe translation shaft 396 and rotation handle 392. The distal portion402 is generally cylindrical (with a greater diameter than the proximalportion) and extends distally from the block portion 404. The rotationhandle 392 extends through the translation handle 394 and has a proximalknob 393 configured for manipulation by a user. The rotation handle isfixedly attached to the central shaft 390, and thus rotation of therotation handle causes rotation of the central shaft 390. The rotationhandle 392 rotates independently of the translation handle 394 in both aclockwise and counterclockwise direction, and turning the rotationhandle 392 in a clockwise direction advances the lock screw 119 into thehousing 172 of the pedicle screw 112. The rotation handle 392 may beprovided with band markers 406 spaced apart at a specific distance (e.g.10 mm) to indicate the amount of reduction. The translation handle 394is provided in the form of a “pistol grip” handle, and includes astationary arm 408 joined with a pivot arm 410 at a first pivot point412. The stationary arm 408 is fixedly connected to the top of theconnector 382. The pivot arm 410 is connected to the stationary arm 408at a first pivot point 412, which comprises the distal ends of both thestationary arm 408 and the pivot arm 410. The pivot arm 410 is alsoconnected to the rotation handle 392 at a second pivot point 414, whichcauses advancement of the central shaft 390 when the pivot arm 410 ismoved. A lock bar 416 is pivotably attached to the pivot arm 410 and isprovided to maintain the translation handle 394 in a locked positionwhen the rod is fully reduced. The lock bar 416 extends through anaperture 418 formed in the stationary handle 408. By way of exampleonly, the lock par 416 may have a ratchet-type engagement with theaperture 418. Other locking engagements are possible.

The translation shaft 396 is mated at its proximal end with the rotationhandle 392 and engages with the central shaft 390 at the proximal sideof the block portion 404. The distal portion 402 of the central shaft390 extends distally from the block portion 404. The distal portion 402extends through a spring (not shown) and an inner sleeve 398. The springis positioned just distally of the block portion 404, between the blockportion 404 and the inner sleeve 398. The spring and inner sleeve 398are contained within an outer sleeve 400. The distal portion 402 of thecentral shaft 390 has a distal rounded reduction end 420 that isconfigured to engage the spinal rod 114 and reduce it into the housing172. Alternatively, the distal reduction end 420 may be a generallyplanar rather than rounded (for example, FIGS. 71-74 illustrate agenerally planar reduction end 361 a). A snap ring 422 is positionedwithin a recess formed just proximally of the distal rounded reductionend 420. The snap ring 422 is sized and configured to prohibit passageof the lock screw 119 until the spinal rod 114 is fully seated in thehousing 172 and an appropriate distal force is applied to the lock screw119 by the inner shaft (as will be explained below). The distal portion420 has a lock screw engagement feature as described above. One or morewindows 424 may be formed in the outer sleeve 400 near the top of theinner sleeve 398. The windows 424 may provide a visual indication (forexample, a color coded indication) of when the rod 114 is fully reducedand the lock screw 119 is in position at the top of the housing 172awaiting engagement. Alternatively, the final band marker 406 may bepositioned to disappear below the stationary handle 408 when the rod isfully reduced. The final band marker 406 may be colored (e.g. green) toaid visualization.

In use, once the pedicle screws 112 have been properly seated and a rod114 introduced, the reduction instrument 380 is engaged to a guideassembly 116 as previously described. At least one lock screw 119 isattached to the lock screw engagement feature of the central shaft 390.The translation handle 394 is operated by squeezing the pivot arm 410,which advances the central shaft 390 in a distal direction such that thedistal engagement end 420 contacts the spinal rod 114. At some pointduring this advancement the lock screw 119 will come into contact withthe top of the housing 172. However, because the central shaft 390 isnot rotating at this point, the distal engagement end 420 continues toadvance through the central aperture 374 of the lock screw 119 while thelock screw 119 remains stationary atop the housing 172. The inner sleeve398, which abuts the lock screw 119 and extends proximally therefrom,consequently also remains stationary during this time as well. However,during this additional advancement (after the lock screw 119 has comeinto contact with the housing 172) the block portion 404 of the centralshaft 390 continues to advance distally. The spring, which is positionedbetween the block portion 404 and the inner shaft 398, compresses due tothe transfer of translational energy from the block portion 404 to thespring. This continues until the spinal rod 114 is fully reduced withinthe housing 172 of the pedicle screw 114. At this point the lock screw119 is in position at top of the housing 172 of the pedicle screw 112,but the complementary guide and advancement features are not yetengaged. To do so, the rotation handle 352 may be briefly rotated in aclockwise or counterclockwise direction to align the guide andadvancement features on the lock screw 119 and housing 172. Though notnecessarily, an audible “click” may be heard, indicating that the guideand advancement features 180,376 have initially mated and are ready forfull installation. The rotation handle 352 is then rotated in aclockwise direction. The engagement of the guide and advancementfeatures combined with the release of the energy contained in thecompressed spring push the lock screw 119 down the central shaft 390 andinto the housing 172. When the lock screw 119 is fully seated, therotation handle 392 will cease to rotate. To effect removal of thereduction instrument 380, the translation handle 394 is briefly turnedcounterclockwise (e.g. 10 mm) to back off reduction. The spring locks344 are disengaged as described above and the reduction instrument 380may be removed from the operative corridor.

FIGS. 78-81 illustrate an example of an alternative reduction instrument430 according to another embodiment of the spinal fixation 110. Thereduction instrument 430 may preferably be used for reduction in asingle-level construct. The reduction instrument 430 is configured foruse with any of the guide assemblies described above (e.g. 18, 116, 188,224), however for the purpose of illustration the reduction instrument430 will be described in use with the guide assembly 116 shown anddescribed in relation to FIG. 21 et seq. By way of example only, thereduction instrument 430 includes a body 432, a handle 434, a fixedattachment assembly 436, and a translating attachment assembly 438. Thebody 432 includes a pair of elongated racks 440 arranged parallel to oneanother and joined at a proximal end by a generally curved connector442. The racks 440 each include a translation slot 444 configured toallow the translating attachment assembly 438 to translate freely inboth the proximal and distal directions. Each translation slot 444includes a plurality of rounded openings 446 configured to allow thetranslating attachment assembly 438 to rest easily in a single selectedposition without inhibiting the overall ability to translate. The handle434 is connected to the curved connector 442 via a shaft 448.

The fixed attachment assembly 436 is positioned between the distal endsof each of the racks 440 and is pivotably attached to each rack 440 viaa swivel pin 450. The translating attachment assembly 438 is positionedbetween the racks 440 and is capable of freely translating therealong.The translating attachment assembly 438 includes a swivel pin 452extending therethrough and having circular ends 454 that engage thetranslation slots 444 and rest in the rounded openings 446. The fixedattachment assembly 436 and translating attachment assembly 438 eachcomprise a connector 456 that attaches to the guide assembly 116 (viathe cap 128). The connector 456 has a guide cavity 458 into which theproximal end 122 of the outer sleeve 118 (featuring the cap 128) isreceived. The proximal end 122 is keyed to the guide cavity 458 so as toprevent rotation of the guide assembly 116 relative to the reductioninstrument 430. Spring locks 460 on the connector 456 are provided toprevent translation of the guide cap 128 and attached guide assembly 116relative to the reduction instrument 430. Specifically, the spring locks460 include ridges 462 that extend through the connector 456 into theguide cavity 458 and engage the circumferential groove 130 situatedbelow the proximal end 122 when the guide assembly 116 is mated with thereduction tool 430. The ridges 462 allow the proximal end 122 of theguide assembly 116 to push past the spring locks 460 until the ridges462 snap into place within the circumferential groove 130. The connector456 has a central aperture 464 formed there to allow passage of a lockscrew driver (not shown). To release the connection between thereduction instrument 430 and the guide assembly 116, the proximal endsof the spring locks 460 can be depressed causing the ridges 462 to liftout of the circumferential groove 130, thus allowing the removal of theconnector 128 from the guide cavity 458.

In use, once the pedicle screws 112 have been properly seated and a rod114 introduced, the reduction instrument 430 is employed by attachingthe fixed attachment assembly 436 to a first guide assembly 116 at afirst vertebral level and attaching the translating attachment assembly438 to a second guide assembly 116 on a adjacent vertebral level. Theattachment assemblies are attached to the guide assemblies in the mannerdescribed above. The handle 434 is then pushed downward (e.g. toward thespine), causing the body 432 to pivot around the translating attachmentassembly 438, thus lifting the fixed translation assembly 436. Thus thescrew 112, guide 116, and ultimately vertebra are lifted upward (i.e.reduced) to the desired position. A lock screw 119 is introduced via alock screw inserter (not shown) and attached to the housing 172 of thepedicle screw 112. The reduction instrument 430 can then be removed andthe lock screw 119 tightened via a final tightening device (not shown).

FIGS. 82-85 illustrate another alternative reduction instrument 470according to still another example embodiment of the spinal fixationsystem 110. Generally, the reduction instrument 470 is used to fullyseat (“reduce”) the spinal rod 114 into the pedicle screw 112 andthereafter insert a lock screw 119 to secure the rod 114 to the screw112. The reduction instrument 470 is configured for use with any of theguide assemblies described above (e.g. 18, 116, 188, 224), however forthe purpose of illustration the reduction instrument 470 will bedescribed in use with the guide assembly 116 shown and described inrelation to FIG. 21 et seq. The reduction instrument 470 includes aconnector 472 that releasably couples the reduction instrument 470 tothe guide assembly 116 (via the cap 128). The connector 472 has a guidecavity 474 into which the proximal end 122 of the outer sleeve 118(featuring the cap 128) is received. The proximal end 122 is keyed tothe guide cavity 474 so as to prevent rotation of the guide assembly 116relative to the reduction instrument 470. Spring locks 476 on theconnector 472 are provided to prevent translation of the guide cap 128and attached guide assembly 116 relative to the reduction instrument470. Specifically, the spring locks 476 include ridges (not shown, butidentical to those described above) that extend through the connector472 into the guide cavity 474 and engage the circumferential groove 130situated below the proximal end 122 when the guide assembly 116 is matedwith the reduction tool 470, The ridges allow the proximal end 122 ofthe guide assembly 116 to push past the spring locks 476 until theridges snap into place within the circumferential groove 130. To releasethe connection between the reduction instrument 470 and the guideassembly 116, the proximal ends of the spring locks 476 can be depressedcausing the ridges to lift out of the circumferential groove 130, thusallowing the removal of the connector 128 from the guide cavity 474.

The reduction instrument 470 includes a reduction assembly 478 and alock screw inserter 480. The reduction assembly includes a reductiontube 482, a threaded shaft 484, and a reduction knob 486. The reductiontube 482 has a proximal end 488, a distal end 490, and a lumen extendingthrough the reduction tube 482 from the proximal end 488 to the distalend 490. The lumen at proximal end 488 is threaded to threadedly engagethe threaded shaft 484, The distal end 490 is configured to engage thespinal rod 114 in two points. The threaded shaft 484 is connected to thereduction knob 486 at its proximal end and the connector 472 at itsdistal end. The connection with the reduction knob 486 is fixed suchthat the rotation of the reduction knob 486 causes the threaded shaft484 to rotate. The connection with the connector 472 is fixed axiallybut not fixed rotationally, such that the threaded shaft 484 freelyrotates against the connector 472 without causing any rotation of theconnector 472. The result of this interaction is that upon rotation ofthe reduction knob 486 (and threaded shaft 484), the reduction tube 482translates in a distal direction relative to the connector 472 (andattached guide assembly 116). The distal end 490 will engage a spinalrod 114 placed within the guide assembly 116 (as described above) andreduce the spinal rod 114 into the pedicle screw 112.

The lock screw inserter 480 extends through the reduction assembly 478lock screw knob 492, a distal engagement post 494, and an elongatedshaft 496 extending between the lock screw knob 492 and distalengagement post 494. The distal engagement post 494 is configured toreceive a lock screw 119, By way of example only, the distal engagementpost 494 has a hexalobe configuration that is complementary to theaperture 374 of the lock screw 119 (FIG. 66 ). The distal engagementpost 494 further includes a snap ring 498 positioned within a recess499. The snap ring 498 prevents premature ejection of the lock screw 119during the implantation process.

In use, once the pedicle screws 112 have been properly seated and a rod114 introduced, the reduction instrument 470 is engaged to a guideassembly 116 as previously described. At least one lock screw 119 isattached to the distal engagement post 494 of the lock screw inserter480. The reduction knob 486 is operated in a clockwise direction (usingan appropriate attachment device) to advance the reduction tube 482 in adistal direction such that the distal engagement end 490 contacts thespinal rod 114. Operation of the reduction knob 486 is continued untilthe rod is fully reduced and seated within the housing 172 of thepedicle screw 112. At this point the lock screw 119 is in position attop of the housing 172 of the pedicle screw 112, but the complementaryguide and advancement features are not yet engaged. To do so, the lockscrew knob 492 may be briefly rotated in a clockwise or counterclockwisedirection until an audible “click” is heard, indicating that the guideand advancement features have initially mated and are ready for fullinstallation. The lock screw knob 492 is then rotated in a clockwisedirection and the lock screw 119 is introduced into the housing 172.When the lock screw 119 is fully seated, the lock screw knob 492 willcease to rotate. To effect removal of the reduction instrument 470, thereduction knob 486 is briefly turned counterclockwise (e.g. 10 mm) toback off reduction. The spring locks 476 are disengaged as describedabove and the reduction instrument 470 may be removed from the operativecorridor.

FIG. 86 illustrates an example of a compression instrument 500configured for use with the spinal fixation system 110 according to oneembodiment of the present invention. By way of example only, thecompression instrument 500 is a fulcrum pistol grip compressor with amain body 502, a rack 504, and a handle 506. The main body 502 includesa track 508 configured to receive the rack 504 and allow translationtherein. The rack 504 is an elongated body configured to be receivedwithin the track 508. The distal end of the rack 504 includes a tubularshaft 510 oriented generally orthogonally relative to the rack 504. Alock screw driver 512 extends through the tubular shaft 510 and isconfigured to be mated with a lock screw 119. The handle 506 ispivotably attached to the main body 502 via a pivot 514. A handle shaft516 extends from the distal end of the handle 506 and is configured tobe received within a guide assembly 116. ‘The lock screw driver 512 andhandle shaft 516 are oriented in a generally parallel manner relative toone another. A push button 518 is provided on the distal end of the mainbody 502 and is configured to release the rack 504 when activated.

The compression instrument 500 may be used when at least one vertebrallevel to be fixed is in need of compression. Prior to using thecompression instrument 500, the pedicle screws 112 are put in place anda spinal rod 114 is seated therein. At one vertebral level, the spinalrod 114 is fully reduced and the lock screw 119 is secured to thepedicle screw. A first guide assembly 116 is attached to the pediclescrew at this first level. At the adjacent level to be compressed, thespinal rod 114 is fully reduced and the lock screw 119 is applied to thepedicle screw but not finally tightened. A second guide assembly 116 isattached to the pedicle screw 112 at this second level. To use thecompression instrument 500, the handle shaft 516 is inserted into thefirst guide assembly 116 and the lock screw driver 512 is inserted intothe second guide assembly 116 such that the distal end 519 of the lockscrew driver 512 engages the lock screw 119. During this insertion, thepush button 518 is depressed so that the rack 504 can move freely withinthe main body 502. This ensures proper alignment of the lock screwdriver 512 and the guide assembly 116, and engagement with the lockscrew 119. When proper alignment is achieved the push button 518 isreleased. The user then squeezes the handle 506, which compresses thevertebra by driving the first and second guide assemblies 116 (andattached screws and vertebrae) toward one another. Once the desiredcompression is achieved, the second lock screw 119 is tightened usingthe lock screw driver 512.

FIGS. 87-89 illustrate an alternative example of a compressioninstrument 520 according to another embodiment of the spinal fixationsystem 110. By way of example only, the compression instrument 520 is arack compressor for compressing the distance between adjacent vertebraprior to locking the spinal rod 114 in both pedicle screws 112. Thecompression instrument 520 includes a rack 522 with a fixed arm 524 anda movable arm 526. The rack 522 includes a plurality of teeth 523provided along one side of the rack 522 and extending substantially thelength of the rack 522. The fixed arm 524 is positioned at a first endof the rack 522 and includes a fixed base 528 that is attached to therack 522 and a removable arm member 530 that includes an attachmentelbow 532, an elongated arm 534, and a hoop 536. The fixed base 528includes a cylindrical post 538 extending laterally from the fixed base528 and a fixed gear wheel 540 at the base of the post 538 and adjacentthe fixed base 528. The attachment elbow 532 extends laterally from theproximal end of the elongated arm 534 and has an aperture 542 andassociated lumen for receiving the post 538. The aperture 542 containsgear slots that mate with the gear wheel 540. The hoop 536 is positionedat the distal end of the elongated arm 534 and is configured foradvancement over a guide assembly 116. The moveable arm 526 includes atranslating base 544 that is capable of translating along the rack 522and a removable arm member 546 that includes an attachment elbow 548, anelongated arm 550, and a hoop 552. The translating base 544 includes acylindrical post 554 extending laterally from the translating base 544and a fixed gear wheel 556 at the base of the post 554 and adjacent thebase 544. The attachment elbow 548 extends laterally from the proximalend of the elongated arm 550 and has an aperture 558 and associatedlumen for receiving the post 554. The aperture 558 contains gear slotsthat mate with the gear wheel 556. The hoop 552 is positioned at thedistal end of the elongated arm 550 and is configured for advancementover a guide assembly 116. This configuration allows the compressor armsto be attached to the rack assembly at a variety of angles.

The translating base 544 includes a user selectable lock 560 thatprevents translation in an undesired direction (e.g. moving arms awayfrom each other when compression is desired and moving arms toward eachother when distraction is desired). The lock 560 includes a selectorswitch 562, a first pawl 564, a second pawl 566. The selector switch 562is pivotably attached to the translating base 544 and includes generallysmooth rounded pawl interface 568 and a recess 570 formed therein. Thefirst pawl 564 is pivotably connected to the translating base 544 andincludes a first end 572 and a second end 574. The first end 572 isgenerally rounded and dimensioned to be received within the recess 570on the selector switch 562. The second end 574 includes a ratchet and isconfigured to engage the ridges 523 of the rack 522 to prevent movementof the translating arm 526 away from the fixed arm 524. The second pawl566 is pivotably connected to the translating base 544 and includes afirst end 576 and a second end 578. The first end 576 is generallyrounded and dimensioned to be received within the recess 570 on theselector switch 562. The second end 578 includes a ratchet and isconfigured to engage the ridges 523 of the rack 522 to prevent movementof the moveable arm 526 toward the fixed arm 524. The translating base544 further includes a turnkey 580 that a user may manipulate to causethe translating arm 526 to translate along the rack 522. The turnkey 580is attached to the translating base 544 and interacts with the teeth 523of the rack 522 via a rotating gear 582.

In use, when the turnkey 580 is operated to move the movable arm 526towards the fixed arm 524 the guide assembly 116 (and thus pedicle screw112 and attached vertebra) that the moveable arm 526 is attached tomoves towards the other one, compressing the distance between theadjacent vertebrae. The principle also works in reverse to distract thevertebrae. The selector switch 562 is configured to adjust the lock 560between a compression position (which allows compression and preventsdistraction), a distraction position (which allows distraction andprevents compression), and an open position (which allows the movablearm 526 to move in either direction along the rack 522). The selectorswitch 562 is configured to point in the general direction of thedesired movement. When the lock 560 is in the compression position, therecess 570 is engaged with the first end 572 of the first pawl 564. Thiswill force the second end 574 to engage the teeth 523 of the rack 522and prevent movement of the moveable arm 526 away from the fixed arm524. Simultaneously, the rounded surface 568 of the selector switch 562forces the first end 576 end of the second pawl 566 (relatively) down,such that the second end 578 is unable to engage the teeth 523 of therack 522. This allows for translation of the moveable arm 526 in thecompression direction while preventing such movement in the distractiondirection. Likewise, when the lock 560 is in the distraction position,the recess 570 is engaged with the first end 576 of the second pawl 566.This will force the second end 578 to engage the teeth 523 of the rack522 and prevent movement of the moveable arm 526 toward the fixed arm524. Simultaneously, the rounded surface 568 of the selector switch 562forces the first end 572 end of the first pawl 564 (relatively) down,such that the second end 574 is unable to engage the teeth 523 of therack 522. This allows for translation of the moveable arm 526 in thedistraction direction while preventing such movement in the compressiondirection. When the selector switch 562 is in the open position, therecess 570 does not engage either of the first and second pawls 564,566. The rounded surface 568 engages the first end 572 of the first pawl564 and also the first end 576 of the second pawl 566, forcing them both(relatively) down. The result is that neither pawl 564,566 is engagedwith the teeth 523 of the rack 522, and the moveable arm 526 is able totranslate in either direction and effect both distraction andcompression.

FIGS. 90-96 illustrate an example of a multi-load lock screw inserter590 configured for use with the spinal fixation system 110 according toone embodiment of the present invention. The multi-load lock screwinserter 590 is useful in that multiple lock screws 119 may be loaded onto the driver 590 such that a user may quickly move among multiple guideassemblies 116 and anchors 112 without having to load a new lock screw119 each time. By way of example only, the multi-load lock screwinserter 590 includes a handle 592 and a central shaft 594 extendingdistally from the handle 592. The multi-load lock screw inserter 590further includes a spring 596, an inner sleeve 598, and an outer sleeve600. The spring 596 is positioned between the handle 592 and the innersleeve 598. The spring is contained within the outer sleeve 600. Thecentral shaft 594 extends through the spring 596, inner sleeve 598, andouter sleeve 600. The proximal end of the inner sleeve 598 abuts thedistal end of the spring 596. The distal end of the inner sleeve 598 isalways in contact with the proximal-most lock screw 119.

The distal portion of the central shaft 594 includes a drive feature 602that is configured to retain and control the rotation of the attachedlock screws 119. By way of example only, the drive feature 602 may havea hexalobe shape, however other shapes that prevent rotation of the lockscrew 119 relative to the central shaft 594 are possible. A snap ring604 is positioned within a recess formed just proximally of the distalend of the central shaft 594. The snap ring 604 is sized and configuredto prohibit passage of the lock screw(s) 119 until an appropriate distalforce is applied to the lock screw 119 by the inner sleeve 598 and/or arotational engagement with a pedicle screw.

In use, as multiple lock screws 119 are loaded onto the multi-load lockscrew inserter 590, the proximal-most lock screw 119 forces the innersleeve 598 in proximal direction, which causes the spring 596 tocompress. As lock screws 119 are engaged to pedicle screws (and removedfrom the multi-load lock screw inserter 590), the spring 596 exerts adistal force on the inner sleeve 598, which in turn pushes the next lockscrew 119 into position. In this fashion, a user may quickly move amongmultiple guide assemblies 116 and anchors 112 without having to load anew lock screw 119 each time.

FIGS. 97-98 illustrate an example of a guide adjuster 610 for use withthe spinal fixation system 110 of the present invention. The guideadjuster 610 is configured for use with any of the guide assembliesdescribed above, however for the purpose of illustration the guideadjuster 610 will be described in use with the guide assembly 116 shownand described in relation to FIG. 21 et seq. The guide adjuster 610 isuseful when the guide assemblies 116 are in need of twisting in order toalign the guide channels. By way of example only, the guide adjuster 610includes a handle 612 and a guide cavity 614. The handle 612 includes apair of arms 616 enabling a user to manipulate the guide adjuster 610.The guide cavity 614 is configured to receive the proximal end 122 ofthe outer sleeve 118 (featuring the cap 128). The proximal end 122 iskeyed to the guide cavity 614 so as to prevent rotation of the guideassembly 116 relative to the guide adjuster 610.

FIGS. 99-100 illustrate an example of a tap guide 620 including a catchmechanism for use with the spinal fixation system of the presentinvention. Generally, the catch mechanism is spring loaded to catch thetap in a contained position (distal end contained within dilator).Pressing the catch release allows the tap to be advanced past the distalend of the dilator. Once the hole is tapped, the tap can be pulled backand again locked in the contained position for removal. By way ofexample only, the tap guide 620 is a generally tubular elongated memberhaving a shaft 622 with a lumen 624 extending therethrough. The outersurface 626 of the shaft 622 includes rifling 628, which facilitatesinsertion into the operative corridor. The proximal end of the shaft 622is equipped with a catch mechanism which includes a retention tab 630, aspring 632, a retaining pin 634, and a catch release button 636. Theretention tab 630 retains the tap (not shown) in the tap guide 620during insertion into and removal from the surgical target site. Thisretention is facilitated by the spring 632. Once docked on the pedicle,the catch release button 636 may be pressed, allowing the tap to passsuch that the distal end of the tap can extend past the end of the tapguide 620 for tapping of the pedicle. The distal end 638 of the shaft622 includes a choke feature which facilitates the alignment of thetool.

FIG. 101 illustrates an example of an offset dilator 640 configured foruse with the spinal fixation system 110 according to one embodiment ofthe present invention. By way of example only, the offset dilator 640includes a tubular shaft 642 having a lumen 644 extending therethrough.A longitudinal groove 646 is formed along the outer surface of theoffset dilator 640 and is configured to receive a K-wire (not shown).The offset dilator 640 may have a shaped proximal end 648 for ease ofmanipulation. The offset dilator 640 may be used to expose the facet fordecortications and fusion. The offset dilator 640 is advanced over theK-wire via the longitudinal groove 646. The offset dilator 640 can thenbe rotated around the K-wire until the lumen 644 is centered over thefacet.

FIGS. 102-103 illustrate an alternative example of an offset dilator 650configured for use with the spinal fixation system 110 according toanother embodiment of the present invention. By way of example only, theoffset dilator 650 includes a tubular shaft 652 having a lumen 654extending therethrough. A longitudinal groove 656 is formed along theouter surface of the offset dilator 650 and is configured to receive aK-wire (not shown). The offset dilator 650 may have a shaped proximalend 658 for ease of manipulation. The offset dilator 650 furtherincludes a lateral slot 659 that is dimensioned to receive a light cable(not shown). The offset dilator 650 may be used to expose the facet fordecortications and fusion. The offset dilator 650 is advanced over theK-wire via the longitudinal groove 656. The offset dilator 650 can thenbe rotated around the K-wire until the lumen 654 is centered over thefacet. Once the offset dilator 650 is in position, a light cable may beemployed in the lateral slot 659 to introduce light to the surgicaltarget site.

FIG. 104 is an example of a secondary dilator 660 positioned within theoffset dilators 640,650 to facilitate advancement to the surgical targetsite. The secondary dilator 660 has an elongated tubular shaft 662 and alumen 664 extending therethrough.

FIGS. 105-108 illustrate an example of an alternative rod inserter 670for use with the spinal fixation system 110 according to anotherembodiment of the present invention. The rod inserter 670 is capable oflockingly engaging the cylindrical body portion of a spinal rod (asopposed to one of the ends). By way of example only, the rod inserter670 includes a handle 672, a shaft sleeve 674, and a shaft 676. Thehandle 672 has an interior lumen 678. The shaft 676 is an elongatedcylindrical member having a proximal threaded region 680 and a distalrod retaining head 682. The proximal threaded region 680 is threadedlyreceived within a rotating knob 684 positioned on the proximal end ofthe handle 672. The distal rod retaining head 682 is formed from a pairof prongs 686 that cooperate to form a semi-cylindrical recess 688 thatis configured to receive a spinal rod (not shown). A small slot 690 isformed in the shaft 676 at the distal end to allow for expansion and/orcontraction of the rod retaining head 682 during rod engagement. Theouter sleeve 674 includes a distal cavity 692 for receiving the rodretaining head 682 when a spinal rod is engaged and the rod inserter 670is in a locked position. The shaft 694 includes a translation slot 694configured to receive a translation pin 696 that is secured to the outersleeve 674. The translation slot 694 and pin 696 combination serve tocontrol and limit the amount of translation the shaft 676 is capable of.By way of example only, the slot 694 allows for approximately 5 mm oftranslation. The rotating knob 684 is secured to the handle 672 by wayof an internal ring 698.

In use, a spinal rod is placed into the recess 688 at the distal end ofthe shaft 676. The rotating knob 684 is turned clockwise, which causesthe shaft 676 to translate in a proximal direction. The distal rodretaining head 682 is then drawn into the distal cavity 692 of the outersleeve 674. This effectively locks the spinal rod to the rod holder 670as the prongs 686 are squeezed together by the distal cavity 692.

FIGS. 109-115 illustrate a compression system 700 configured for usewith the spinal fixation system 110 according to an example embodiment.Compression system 700 is advantageous when guide towers are crossed orare otherwise not in line, which makes the use of a rack based orpivoting compression instrument challenging or impossible. By way ofexample, the compression system 700 includes a rotational tool 702, apivot tool 704, and a hinged tool 706 (FIG. 114 ). The hinged tool 706is optional and may be used in lieu of the pivot tool 704 whenpositioning of the guides makes inserting the pivot tool over the guideschallenging.

Referring to FIG. 109 , the rotational tool 702 includes a handle member710, a stem 712 extending distally from the handle member 710, and adistal paddle 714 extending distally from the stem 712. The handle 710includes a contoured gripping surface for handling by a user. The stem712 extends linearly from the handle 710 and has a longitudinal axisthat is coaxial with the longitudinal axis of the handle 710. The distalpaddle 714 has a generally elliptical perimeter and a longitudinal axisthat is angularly offset from the longitudinal axis of the stem 712. Thedistal paddle 714 includes a first opening 716 and a second opening 718positioned proximally of the first opening 716. The first opening 716 isgenerally circular in shape and is sized to snugly receive a first guidetower 708 therein. The second opening 718 is generally elliptical inshape and is dimensioned to receive a second guide tower 708 therein.The elliptical shape of the second opening 716 allows the second guidetower to move within the opening 716 in response to force applied to therotational tool 702 by a user.

Referring to FIG. 110 , the pivot tool 704 includes a handle member 718,a stem 720 extending distally from the handle member 718, and a distalpaddle 722 extending distally from the stem 720. The handle 718 includesa contoured gripping surface for handling by a user. The stem 720extends linearly from the handle 718 and has a longitudinal axis that iscoaxial with the longitudinal axis of the handle 718. The distal paddle722 has a generally elliptical perimeter and a longitudinal axis that iscoaxial with the longitudinal axis of the stem 720. The distal paddle722 includes a first opening 724 and a second opening 726 positionedproximally of the first opening 724. The first and second openings 724,726 are each generally circular in shape and sized to snugly receive afirst and second guide towers 708 therein. The circular shape and snugengagement of the of the first and second openings 724, 726 preventsboth guide towers 708 from moving relative to the pivot tool 704 whenforce applied by a user.

The paddle 714 of the rotational tool 702 and the paddle 722 of thepivot tool 704 each have unbroken enclosed perimeters. Thus, the onlyway to position a guide tower in either the first or second openings isthe slide the tool over the top of the towers. In some circumstances itmay be advantageous to be able to attach the pivot tool to the towerswithout having to slide them over the top of the towers. In such acircumstance (or otherwise if the user so desires) a hinged tool 706 maybe used in place of the pivot tool 704. The hinged tool 706 comprises afirst arm member 728 and a second arm member 730 hingedly coupledtogether by a distal hinge 732. The first arm member 728 has a proximalportion 734 including a contoured surface for manipulation by a user.The first arm member 728 further includes a distal portion 736 includingan inner facing surface having a first concave portion 738 and a secondconcave portion 740. The second arm member 730 has a proximal portion742 including a contoured surface for manipulation by a user. The secondarm member 730 further includes a distal portion 744 including an innerfacing surface having a first concave portion 746 and a second concaveportion 748. When the hinged tool 706 is in the closed position, thefirst concave portion 738 of the first arm member 728 and the firstconcave portion 746 of the second arm member 730 act in concert to forma generally circular opening 750. Likewise, the second concave portion740 of the first arm member 728 and the second concave portion 748 ofthe second arm member 730 act in concert to form a generally circularopening 752. Openings 750, 752 are dimensioned to snugly receive guidetowers 708 therein.

In use, the compression system 700 is useful for enacting compression atvertebral levels that might otherwise be inaccessible for compressionbecause the guides are converging or crossed altogether, for example atthe L5-S1 level of the spine. Once the guide towers 708 are attached tothe bone screws and the surgeon has a need to compress or distract thevertebrae, the first step is to engage the pivot tool 704 (or hingedtool 706) with the guide towers 708, 708′. When performing compressionor distraction using the compression system 700, one of the guide towers708 remains stationary while the other guide tower (denoted 708′ inFIGS. 112-115 ) moves in response to the force applied by the user. Thepivot tool 708 is positioned such that the guide tower 708 that is toremain stationary is placed within the first opening 724, which is thedistal-most opening. The guide tower that is allowed to move is placedwithin the second opening 726 (the proximal-most opening). The pivottool 704 is advanced distally along the guide towers 708, 708′ until itis placed in the desired pivot point. Most often, this pivot point willbe immediately adjacent the patient's skin, as a lower pivot point willallow more torque to be applied to the guide tower 708′. The rotationaltool 702 is then engaged with the guide towers 708, 708′ at the mostproximal location possible (to ensure that the user has the maximumtorque available). Since guide tower 708 in the present example is toremain stationary, it is placed within first opening 716 (thedistal-most, circular opening). Accordingly, guide tower 708′ ispositioned within the second opening 718 (the proximal-most, ellipticalopening). Compression or distraction is then achieved by maneuvering thehandles 710, 718 either toward or away from each other. If compressionis desired, then the user rotates the handles 710, 718 toward oneanother (direction D₁ in FIG. 115 ). If distraction is desired, then theuser rotates the handles 710, 718 away from one another (direction D2 inFIG. 115 ). Once the desired compression (or distraction) is achieved,the user then holds compression (and distraction) while provisionallytightening the set screw in the housing of the bone anchor. Thecompression system 700 is then completely removed and the sets crew maybe final-tightened using an appropriate instrument.

FIGS. 116-122 illustrate a compression instrument 760 configured for usewith the spinal fixation system 110 according to another exampleembodiment. As with compression system 700, compression instrument 760is advantageous when guide towers 761, 761′ are crossed or are otherwisenot in line, which makes the use of a rack based or pivoting compressioninstrument challenging or impossible. By way of example, the compressioninstrument 760 includes a compressor body 762, a first handle member 764integrally formed and extending away from the compressor body 762, and asecond handle member 766 hingedly attached to the compressor body 762.

The compressor body 762 includes a base 768 and an elongated post 770extending distally from the bottom portion of the base 768, Theelongated post 770 is generally cylindrical in shape and is configuredfor insertion into the lumen of a stationary guide tower 761 (FIG. 121). The first handle member 764 is an elongated member extendinglaterally away from the base 768, preferably at an upward angle relativeto the elongated post 770. That is, the angle that is formed between thefirst handle member 764 and the elongated post 770 is preferably obtuse.A generally rectangular aperture 772 is formed in the first handlemember 764 as a vertically-oriented through-hole. The aperture 772 isdimensioned to receive a ratchet bar 774 extending from the secondhandle member 766. The aperture 772 further includes a ridged or angledsurface (not shown) adapted to engage ratchet teeth 776 on the ratchetbar 774 to enable the compression instrument 760 to hold compression ifdesired by the user. To release compression, the ratchet bar 774 issimply manually disengaged from the ridged or angled surface within theaperture 772. A pair of lateral posts 778, 778′ are positioned at theintersection of the base 762 and the first handle member 764. Thelateral posts 778, 778′ are positioned on opposite sides of the firsthandle member 764 and extend generally perpendicularly away from thehandle member 764.

The second handle member 766 has a base 780 and a handle arm 782extending away from the base 780. The base 780 includes a distal end 784and a large central aperture 786 sized and configured to receive thebase 768 of the compressor body 762. A pair of lateral posts 788, 788′are positioned on either side of the base 780 and extend generallyperpendicularly away from the base 780. A pair of hinge apertures 790are located on the proximal end of the base 780 and are configured toreceive a hinge pin 792, which hingedly connects the second handlemember 766 to the compressor body 762. A grip stop 794 projects upwardfrom the top surface of the handle arm 782 and is configured to providea bumper for a user's hand to help ensure the user's grip does not slipduring use. A resistance member 796 is attached to the bottom surface ofthe handle arm 782 and mates with a resistance member 798 that isattached to the upper surface of the first handle member 764. The matedresistance members 796, 798 bias the first and second handle members764, 766 apart with a force that is relatively easily overcome by auser's hand.

FIGS. 121 and 122 illustrate the compression instrument 760 beingemployed during an example surgical procedure. Before the compressioninstrument 760 is used, however, the user must first final tighten theset screw in guide tower 761 (i.e. the stationary guide. A set screw maybe engaged (loosely) to the anchor that guide tower 761′ is attached to(i.e. the guide spanning the level(s) to be compressed). The compressioninstrument 760 is then employed by inserting the elongated post 770 intothe guide tower 761. Guide tower 761′ is then positioned adjacent thecompression instrument 760, between one set of lateral posts (i.e.lateral posts 778, 788 or lateral posts 778′, 788′). The compressor body762 may be equipped with laser markings or other visual indicia to aidthe user in choosing a correct orientation fix guide 761′. The user thencompresses as needed by squeezing the first and second handle members764, 766 together. This causes the second handle member 766 to hingedlyrotate, which in turn causes the lateral posts 788, 788′ to be pulledinto the guide tower 761′. Since the other lateral posts 778, 778′ arestationary, they act as a fulcrum to the guide tower's lever, causingthe distal end of the guide tower, and consequently the bone anchor andthe vertebral body it is implanted in to be compressed. Compression isheld while a setscrew is provisionally tightened in the compressed boneanchor. The compression instrument 760 is removed before the setscrew isfinal tightened using an appropriate instrument.

FIGS. 123-136 illustrate a compression instrument 800 according toanother example embodiment. By way of example only, the compressioninstrument 800 is a rack compressor for compressing the distance betweenadjacent vertebra. Compression is performed after locking the spinal rod114 in one pedicle screw 112 but prior to locking the spinal rod 114 inthe pedicle screws 112 spanning the vertebral bodies to be compressed.The compression instrument 800 includes a pair of tower extensions 802,a ratcheting rack assembly 804, a thumb key driver 806, and a lockingrack assembly 808.

With reference to FIGS. 125-126 , the tower extension 802 will bedescribed in further detail. Tower extension 802 has a base portion 810and an extension portion 812 extending proximally away from the baseportion 810. The base portion 810 is configured to attach to theproximal end of a guide tower 801. 801′ that is already coupled to aspinal anchor implanted in a vertebral body. The base portion 810 is agenerally tubular member having a interior lumen 814 dimensioned to fitover the top of a guide tower 801. The exterior of the base portion 810further includes a locking clip 816 positioned in a recess 818 and afirst post 820 mounted opposite the locking clip 816 and extendingperpendicularly away from the tower extension 802. The outer surface ofthe locking clip 816 includes a set of ridges 822 or other surfaceroughening to provide a user some frictional purchase to enable use. Theinner surface of the locking clip 816 opposite the ridges 822 includes agenerally circular recess for receiving a portion of a bias spring (notshown) therein. The locking clip 816 is pivotally connected to the base810 via pivot pin 824.

The inner surface of the lower portion of the locking clip 816 includesan attachment feature (not shown) that extends generally perpendicularlyfrom the inner surface and is configured to engage an attachment featureon the guide tower 801, for example a circumferential recess positionednear the proximal end of the guide tower 801. To enable this engagement,the recess 818 includes an aperture formed therein and extending betweenthe outer surface of the base portion 810 and the lumen 814. Theattachment feature may include a distal-facing tapered surface that isinwardly tapered so as to automatically deflect the attachment featureoutward as the top of the guide tower 801 (for example) is advanced intothe lumen 814, permitting the attachment feature to pass the top of thetower 801 until it engages a suitable attachment area thereon. Asdeflection occurs (by the attachment feature being physically pushedaside by the top of the guide tower 801), the locking clip 816 pivotsabout the pivot pin 824, causing the upper portion of the locking clip816 to be received further in the recess 818. Once the top of the toweradvances past the attachment feature, the attachment feature encountersthe circumferential recess (for example). The spring acts on the upperportion of the locking clip 816 causing the locking clip 816 to pivotabout the pivot pin 824 in the opposite direction, urging the attachmentfeature into the recess, which secures the tower extension 802 to theguide tower 801. This way, the tower extension 802 can be positionedover the guide tower 801 and quickly snapped onto and secured to thetower with the simple application of downward pressure. To laterdisengage the tower extension 802 from the guide tower, the user simplyneeds to apply a compressive force (e.g. using a thumb and forefinger)on the ridged portion 822 of the locking clip 816. This will cause thelower portion of the locking clip 816 to pivot outward and disengage theattachment feature from the circumferential recess. The tower extension816 may then be removed from the area.

The proximal end of the extension portion 812 includes a second post 826mounted directly above the first post 820. As will be explained, thefirst post 820 is configured to mate with the locking rack assembly 808and the second post 826 is configured to mate with the ratcheting rackassembly 804 such that the locking rack assembly 808 and ratcheting rackassembly are locked to the extensions but are permitted to rotate orpivot relative to them.

The ratcheting rack assembly 804 includes a rack 828, fixed attachmenttab 830, and a translating base 832. The rack 828 includes a pluralityof teeth 834 provided along one side of the rack 828 and extendingsubstantially the length of the rack 828. The fixed attachment tab 830is positioned at one end of the rack 828 and includes a flange 836extending vertically away from the rack 828. The flange 836 includes anattachment aperture 838 configured to receive the second post 826 of thetower extension 802 positioned on the fixed guide 801.

The translating base 832 includes an attachment aperture 840 configuredto receive the second post 826 of the tower extension 802 positioned onthe guide 801′ spanning the level to be compressed. The translating base832 further includes a user selectable lock 842 that preventstranslation in an undesired direction (e.g. toward the fixed end whencompression is desired and away from the fixed end when distraction isdesired). The lock 842 includes a selector switch 844, a first pawl 846,and a second pawl 848. The selector switch 844 is pivotably attached tothe translating base 832 and includes generally smooth rounded pawlinterface 850 and a recess 852 formed therein. The first pawl 846 ispivotably connected to the translating base 832 and includes a first end854 and a second end 856. The first end 854 is generally rounded anddimensioned to be received within the recess 852 on the selector switch844. The second end 856 includes a ratchet and is configured to engagethe ridges 834 of the rack 828 to prevent movement of the translatingbase 832 away from the fixed end. The second pawl 848 is pivotablyconnected to the translating base 832 and includes a first end 856 and asecond end 858. The first end 856 is generally rounded and dimensionedto be received within the recess 852 on the selector switch 844. Thesecond end 858 includes a ratchet and is configured to engage the ridges834 of the rack 828 to prevent movement of the translating base 832toward the fixed end.

The translating base 832 further includes a turn key aperture 860configured to receive a turn key driver 806 therein that a user maymanipulate to cause the translating base 832 to translate along the rack834. The turn key driver 806 removably engages the translating base 832and interacts with the teeth 834 of the rack 828 via a rotating gear862. As shown in FIG. 128 , the turn key driver 806 proximal handle 864and a distal gear shaft 866 that engages the rotating gear 862.

The locking rack assembly 808 includes rack 868, a fixed attachment tab870, and a locking base 872. The rack 868 includes a plurality of teeth874 provided along one side of the rack 868 and extending substantiallythe length of the rack 868. The fixed attachment tab 870 is positionedat one end of the rack 868 and includes a flange 876 extendingvertically away from the rack 868. The flange 876 includes an attachmentaperture 878 configured to receive the first post 820 of the towerextension 802 positioned on the fixed guide 801.

The locking base 872 includes an attachment aperture 880 configured toreceive the first post 820 of the tower extension 802 positioned on theguide 801′ spanning the level to be compressed. The locking base 872further includes a lower channel 871 that houses the rack, a userselectable lock 882 that prevents translation in either direction whenthe lock is engaged, and an upper housing 873 including sidewalls 875 tocontain the various components of the lock 882. The lock 882 includes aselector switch 884, pawl 886, and a locking pin 888. The selectorswitch 884 is slidably attached to the translating base 872 and ismoveable from a first position in which the locking base 872 is unlockedto a second position in which the locking base 872 is locked. Theselector switch includes base surface 877, a superior flange 879, and apair of inferior flanges 891 positioned on opposing sides of the basesurface 877 and extending inferiorly so as to extend along the exteriorof the sidewalls 875. The pawl 886 is pivotably connected to the lockingbase 872 via a pivot pin 887 extending between the sidewalls 875 andincludes a first end 890 and a second end 892. The first end 890 has aninferior notch so as to form a ledge dimensioned engage the locking pin888 when the selector switch 884 is in the locked position. The secondend 892 includes a ratchet and is configured to engage the ridges 874 ofthe rack 868 to prevent movement of the locking base 872 in anydirection when the selector switch 888 is in the locked position. Thelocking pin 888 is attached to and spans between the inferior flanges891 of the selector switch 884 and extends through a horizontal slot 894formed in each of the sidewalls 875. The horizontal slot 894 is orientedso that one end of the slot 894 is underneath the first end 890 of thepawl. When the selector switch 884 is moved from an unlocked position toa locked position, the locking pin 888 moves with it along thehorizontal slot 894 until it rests at the end of the slot 894 underneaththe first end 890 of the pawl 886, preventing the pawl 886 frompivoting. In this position, the second end 892 is unable to disengagefrom the ratchet teeth 874 and thus the locking base 872 is unable tomove in any direction.

The outside surface of the sidewalls 875 may include one or more visualindicators 896 that help alert the user as to which position the lockingbase 872 is in (i.e. locked or unlocked). By way of example, the visualindicators 896 may include color-coded indicia. By further example thecolor-coded indicia may include green and red panels, where the redpanel located in an area that is covered by the inferior flanges 891when the locking base 872 is unlocked while simultaneously the greenpanel is located in an area that is not covered by the inferior flanges891, thereby giving the user visual indication that the locking base 872is unlocked. Sliding the selector switch 884 into the locked positioncauses the inferior flanges 891 to cover the green panel and expose thered panel, indicating that the locking base 872 is now locked.

In use, the user must first determine whether compression or distractionis needed. If compression is needed, then the user should preferablybegin with the guide towers slightly toed in at the top of the rack. Thelocking rack is locked to create a pivot point by sliding the selectorswitch to the locked position as described above. The selector switch onthe ratcheting rack is then set to in the direction that will allowcompression by increasing the distance between the top of the guides andcausing the distal end of the guide to pivot towards each other. Theturn key driver is then rotated clockwise causing the ratcheting rack toseparate which pivots the distal end of the guides towards until thedesired compression is received. For distraction, the user begins withthe towers slightly toed out at the top of the rack (FIG. 134 ). Thelocking rack is locked in position to establish the pivot point, and theselector switch on the ratcheting rack is put in the position thatallows for distraction by drawing the top of the guides closer togetherwhich causes the distal end of the guides to pivot away from each other.The turnkey driver may then be turned counterclockwise to effectdistraction.

With reference to FIGS. 135 and 136 , it is also possible to use thelocking rack assembly 808 to achieve compression or distraction withoutthe ratcheting rack assembly 804. Instead, the locking rack may be usedas previously described to establish a pivot point between the guides,and a simple hinged compressor 899 can be used to apply force to theguides. For example, as shown in FIG. 135 to distract the locking rackassembly 808 is locked with the guides slightly toed out above the rack.The hinged compressor 899 is positioned above the locking rack andcompresses the guides together to cause the distal ends of the guides topivot away from each other. Conversely, as depicted in FIG. 136 , tocompress the locking rack assembly is locked with the guides slightlytoed in above the rack. The hinged compressor 899 is positioned belowthe locking rack and compresses the guides together causing the distalends of the guides to pivot towards each other.

FIG. 137 illustrates a combination awl-tap 900 according to an exampleembodiment. The combination awl-tap 900 of the instant exampleeliminates the need for a K-wire prior to tapping a screw hole. By wayof example only, the combination awl-tap 900 includes an elongated shaft902 having a proximal end 904 and a distal end 906, The proximal end 902includes engagement structure for engaging a handle 908. The distal end906 comprises a shank a proximal portion 910 and a distal portion 912.The proximal portion 910 of the shank includes a threaded region 914configured to tap a thread into the screw hole. This constitutes the tapportion of the awl-tap combo. The distal portion 916 of the shankcomprises a nonthreaded portion having a sharp tip. This constitutes theawl portion of the combination. In addition to the shaft 902 and handle908, the combination awl-tap 900 may include a center needle 918attached to the handle 908 and extending through the interior of theshaft 902.

By way of example, the combination awl-tap 900 may be used by firstinserting the combination awl-tap 900 through a tap guide 620 as shownin FIG. 139 and described above in relation to FIGS. 99-100 . Thecombination awl-tap 900 and tap dilator 620 is advanced to a targetpedicle. The user pushes the catch release button 636 to release theawl-tap combo and enable it to access the pedicle. Using a mallet (orother suitable instrument), the user urges the awl portion of thecombination awl-tap 900 into the pedicle. Approximately 15 mm into thepedicle, the threads of the tap portion 914 will engage the bone. Theuser can then rotate the handle 908 to thread the tap portion 914 intothe bone. Once the tap portion 914 has reached the desired depth, theuser may remove the center needle 918 and insert a K-wire. The tapportion 914 is then unthreaded and the combination awl-tap 900 isremoved from the surgical site.

FIGS. 140-152 illustrate a split-tube retractor 920 according to anexample embodiment. The split-tube retractor 920 of the instantembodiment includes a first retractor arm 922, second retractor arm 924,actuator assembly 926, first retractor blade 928, second retractor blade930, and a handle 932. The first retractor arm 922 has a proximal end934, distal end 936, and a central portion 938 between the proximal anddistal ends. The proximal end 934 includes a threaded aperture 940dimensioned to receive an attachment ring 942 therein. By way of exampleonly, the attachment ring 942 may be used to attach any suitableequipment, such as for example an articulating arm (not shown). Thedistal end 936 includes a blade aperture 944 for attaching a retractorblade (e.g. first retractor blade 928) and a button aperture 946 forhousing a blade release button 948 therein. A lateral flange 950 ispositioned adjacent the button aperture 946 and extends laterally towardthe second retractor arm 924. The lateral flange 950 includes a hingeaperture 952 configured to receive a pivot pin 954 therein. The centralportion 938 includes a recess 956 formed in the underside of the firstretractor arm 924 that is sized and configured to house the actuatorassembly 926 therein. The central portion 938 further includes anaperture 957 formed in the top surface and extend through to the recess956. The edge of the plate that forms the lip of the apertureconstitutes an overhang 959, which interacts with the circumferentialrecess 1012 of the actuator nut 1002 to secure the actuator nut 1002 tothe first retractor arm 922.

The second retractor arm 924 has a proximal end 958, distal end 960, anda central portion 962 between the proximal and distal ends. The proximalend 958 includes a threaded aperture 964 dimensioned to receive anattachment ring 942 therein. The distal end 960 includes a bladeaperture 966 for attaching a retractor blade (e.g. second retractorblade 930) and a button aperture 968 for housing a blade release button970 therein. A lateral recess 972 is positioned adjacent the buttonaperture 968 and is configured to receive the lateral flange 950 of thefirst retractor arm 922. Flanking the lateral recess 972 is a pair offlanges 974 having hinge apertures 976 formed therein and configured toreceive the pivot pin 954 therein. Thus, the interaction between thelateral flange 950 of the first retractor arm 922, lateral recess 972 ofthe second retractor arm 924, and the pivot pin 954 result in a hingedcoupling of the first and second retractor arms 922, 924. The centralportion 962 includes a protrusion 978 extending laterally toward thefirst retractor arm 922. The protrusion 978 includes a slot 980 formedtherein for receiving the inferior aspect of the I-bolt 994. A connectorpin (not shown) extends through the base of the I-bolt 994 and into pinapertures 982 positioned on either side of slot 980 to secure the I-bolt994 to the second retraction arm 924 (by way of protrusion 978).

FIG. 147 illustrates the release button 948/970 in greater detail.Release button 948 is identical to release button 970 so the variousfeatures will be described in relation to release button 948 but applyequally to release button 970. Release button 948 has a button head 984and a post 986 extending distally below the button head 984. The distalend of the post 986 has a recess 988 and upper-facing ridge forming acatch 990 that interacts with a similarly formed and complementary catchon the retractor blade. A spring 992 coils around the post 986, andfunctions to bias the release button 970 so that the catch 990 remainsengaged with the catch 1022 of the retractor blade until the releasebutton 948 is depressed. When that happens, the catches are released,and the blades can be removed from the blade apertures 944, 966.

FIG. 148 illustrates the I-bolt 994 that forms part of the actuatorassembly 926. The I-bolt 994 includes a head 996 and a threaded shank998 extending proximally from the head 996. The head further includes alateral through-hole 1000 configured to receive a connector pin toconnect the I-bolt 994 to the second retractor arm 924. FIG. 149illustrates the actuator nut 1002 that forms part of the actuatorassembly in greater detail. The actuator nut 1002 includes a head 1004,a driver recess 1006, an upper lip 1008, a lower lip 1010, and acircumferential recess 1012. The head 1004 is sized and dimensioned tobe mated with a drive tool, whether using the driver recess 1006 formedin the top of the head 1004 or the contoured side surface 1014 to gripwith an instrument (or the user's hand). The actuator nut 1002 is placedwith the aperture 957 of the first retractor arm 922 such that upper lip1008 extends beyond the aperture lip 959 to contact the upper surface ofthe retractor arm 922. Simultaneously, the lower lip 1010 extends beyondthe aperture lip 959 to contact the underside of the overhang. Thecircumferential recess 1012 is then fully contained within the aperture957. As a result, the actuator nut 1002 is securely mated with theaperture 957 but is free to rotate. The I-bolt 994 cannot rotate due tothe connector pin securing it to the second retractor arm 924. However,as the actuator nut 1002 rotates, the threaded engagement with theI-bolt 994 causes the I-bolt 994 to translate along the threadedportion. Because the second retractor arm 924 is connected to the I-bolt994, the second retractor arm 924 will move in response to the I-bolt924 movement. And further, since the first retractor arm 922 is hingedlycoupled to the second retractor arm 924, the first retractor arm 922will also move in response to the I-bolt 924 movement. Thus, when theactuator assembly 926 is operated by engaging a driver (not shown) withthe driver recess 1006 and rotating counterclockwise, the I-bolt 994translates outward, pushing on the lateral protrusion 978 of the secondretractor arm 924. This causes the second retractor blade 930 to splayoutward, which in turn causes the first retractor blade 928 to splayoutward. Conversely, clockwise rotation of the actuator nut 1002 causesthe blades to come together. If one of the retractor blades is attachedto an articulating arm, then that blade will remain still and only theother blade will move.

FIGS. 150-152 illustrate a retractor blade 930 in greater detail. Firstand second retractor blades 928, 930 are virtually identical save forbeing mirror images of one another, so any feature described withrespect to one of the retractor blades applies to each retractor blade.Retractor blade 930 includes an arm member 1016 and a blade member 1018extending distally from the arm member 1016. The arm member 1016 furtherincludes an attachment post 1020 extending away from the arm member1016. The attachment post 1020 includes a recess and a lip that form acatch 1022 that is configured to mate with the catch 990 of the releasebutton 970 as described above. The attachment post 1020 further includesa generally square-shaped base portion 1024, which interacts with thegenerally square-shaped opening of the blade aperture 966 to help ensurethe retractor blade 930 doesn't rotate independently of the retractorarm 924. The blade member 1018 has a cutaway portion 1026 on one sidefor increased visualization by allowing the user to angle instrumentsout from between the blades. The blade member 1018 also includes aplurality of channels 1028 on the external surface of the blade that areconfigured to receive a K-wire therethrough. A track 1030 extends alongthe inside surface of the blade and is configured to attach accessoriessuch as a light cable or shim.

By way of example, the split-tube retractor may be especially wellsuited facet preparation in conjunction with the application of aminimally invasive fixation construct. To utilize the split-tuberetractor over a K-wire, the pedicle caudal to the facet is targetedwith a K-wire and dilators are advanced over the K-wire. According toone example, the dilators may be only half circles such that dilationextends in only a single direction, towards the facet. The split bladeretractor may then be advanced with the K-wire passing through one ofthe blade cannulations. With the retractor oriented such that thenon-articulating blade (i.e. the blade attached to retractor arm 924without the articulating assembly) is on the K-wire, the articulatingblade will open over the target facet joint. Once docked, split tuberetractor that is advanced over the K-wire may be coupled to the tablemount and the blades articulated open. A light source may be advanceddown the blade. The Facet may then be decorticated and graft materialplaced.

When performing spinal fixation techniques like some of those describedherein, one problem that arises is that often times different types ofscrews require the use of several different drivers during oneprocedure. Referring first to FIGS. 158 and 159 , a polyaxial pediclescrew 1038 (FIG. 158 ) and a polyaxial reduction screw 1040 (FIG. 159 )are shown by way of example for the purposes of illustration. Thepedicle screw 1038 has a threaded shank 1042 and a rod housing 1044. Thethreaded shank has a head portion (not shown) that is nesting in thebase of the rod housing. The head has a hexalobe shaped (for example)drive recess configured to mate with a distal tip of a screwdriver. Theupper arms of the rod housing 1044 have an interior threaded region thatis primarily intended to receive a lock screw therein, however thethreaded region can serve another purpose such as providing a secondaryengagement for the screw driver. The screwdriver may have an additionalengagement feature in the form of a distal insert having wings thatengage the rod channel. The result is a screwdriver that can stabilizethe rod housing 1044 while simultaneously driving the shank 1042. Thepolyaxial reduction screw 1040 also has a threaded shank 1046 and a rodhousing 1048. As with the pedicle screw 1038, the reduction screw 1040has threads at the top of the rod housing 1048 and a drive recess in thehead of the shank 1046. However, a problem arises in that the distancebetween the drive recess at the top of the shank and the threaded regionat the top of the tulip is much greater than with the pedicle screw. Asa result, often times the surgeon is forced to change screwdrivers toaccommodate one of them. This can be time consuming if the particulartechnique calls for a lot of these different types of screws.

FIGS. 153-159 illustrate a screwdriver 1050 according to one exampleembodiment that is capable of driving multiple types of screws with thesame driver, and in particular is capable of having a 3-way engagementwith both pedicle screws and reduction screws. The screwdriver 1050includes an inner shaft 1052, inner sleeve 1054, and outer sleeve 1056.The inner shaft 1050 has a proximal end 1058, middle portion 1060, anddistal end 1062. The proximal end 1058 includes a shaped end 1064configured for attachment to a suitable instrument or other attachment.The distal end includes a shaped driver 1066, for example a hexalobedriver that is configured to interact with the driver recess of theshank 1042 of a polyaxial pedicle screw 1038 (FIG. 158 ) and the driverrecess of the shank 1046 of the polyaxial reduction screw 1040 (FIG. 160).

The inner sleeve 1054 has a distal end 1068, a proximal end 1070, and acentral lumen 1072 extending through the instrument. The distal end 1068has a threaded region 1074 that is configured to mate with the threadson the inside top of the rod housing 1044 of polyaxial pedicle screw1038 (FIG. 158 ) and the threads on the inside top of the rod housing1048 of the polyaxial reduction screw 1040 (FIG. 160 ). The proximal end1070 includes a housing unit 1076 and a spring-biased release button1078, which will be discussed in greater detail below.

FIG. 155 is a close up view of the distal tip of the assembledscrewdriver 1050. Nestled in between the inner shaft 1052 and the innersleeve 1054 is a rod channel engagement piece 1080. The rod channelengagement piece 1080 (shown in isolation in FIG. 156 ) includes anouter ring 1082 having a pair of opposing flanges 1084 and a tubularshaft 1086 extending proximally of the outer ring 1082. The outer ring1082 is sized and configured to snugly fit within the rod housings 1044,1048 without engaging the threads. The flanges 1084 are sized andconfigured to extend into the lower portion of the rod channel at thebase of the housings 1044, 1048. The rod channel engagement piece 1080prevents the rod housing from rotating when driving the screw. Thetubular shaft 1086 is configured to extend the rod channel engagementpiece 1080 so that the outer ring 1082 can still rest at the base of therod channel in the rod housing 1048 of the reduction screw 1040.

FIG. 157 is a close up view of the middle part 1060 of the inner shaftin conjunction with the proximal end 1070 of the inner sleeve 1054 withthe housing unit 1076 removed for clarity. The release button 1078 has afront-facing user interface 1086 and a block 1088 extending laterallybehind the user interface 1086. The block 1088 has an aperture 1090through which the inner shaft 1052 extends. A spring 1092 positionedbehind the block 1088 biases the block 1088 outward in a lockedposition. The block 1088 as shown in FIG. 157 is received with a recess1094 formed in the inner shaft 1052. A second recess 1096 is positionedproximally of the first recess 1094 at a distance that corresponds tothe difference in size between the rod housing 1044 of the pedicle screw1038 and the rod housing 1048 of the reduction screw 1040. As such, auser may adjust the arrangement of the distal portions of the innershaft 1052 and inner sleeve 1054 by pressing the release button 1078.This compresses the spring 1092 and dislodges the aperture 1090 from therecess 1094. The user then urges the inner shaft 1052 forward until theblock 1088 snaps into the second recess 1096. At this point the distaltip of the inner shaft 1052 (with the hexalobe driver) and the rodchannel engagement piece 1080 will be extending a greater distance awayfrom the distal end of the inner sleeve 1054 (with the threadedsurface), which will correspond to the difference in size between therod housing 1044 the pedicle screw and the rod housing 1048 of thereduction screw 1040.

Optionally, a locking apparatus may be employed to cause the inner shaft1052 to automatically stop turning in the event that the screw isadvanced too far. With continued reference to FIG. 157 , a lockingfeature 1098 is provided proximally of the release button 1078. Thelocking feature 1098 includes a superior locking unit 1100 and aninferior locking unit 1102. The superior locking unit has a toothed ring1106 that is configured to engage toothed ring 1108 of the inferiorlocking unit 1102. A spring 1104 acts to draw the superior and inferiorlocking units 1100, 1102 together as the inner shaft 1052 rotates (asthe screw is being driven by the screwdriver 1050). When the toothedrings 1106, 1108 engage one another the inner shaft 1052 will no longerbe able to rotate and advancement of the screw ceases.

FIGS. 160-161 illustrate a K-wire holder 1110 according to an exampleembodiment for use with the various fixation systems disclosed herein.When performing a multi-level spine surgery with a plurality of screws,often there are a lot of K-wires in use, and they can be a nuisance andin the way as the surgical personnel work around them. The K-wire holder1110 offers an effective way to keep the K-wires under control withoutdisrupting the surgery every time a K-wire needs to be added or removedfrom the holder 1110.

By way of example only, the K-wire holder includes a superior clamp body1112 and an inferior clamp body 1114. The superior clamp body 1112 has apair of recesses 1116 configured to hold a pair of silicone inserts1118. By way of example only, the silicone inserts 1118 may have metal(or plastic or other suitable material) bases 1120. Similarly, theinferior clamp body 1114 has a pair of recesses 1122 configured to holda pair of silicone inserts 1124. By way of example only, the siliconeinserts 1124 may have metal (or plastic or other suitable material)bases 1126. When assembled, the opposing silicone inserts 1118, 1124flushly contact one another to form a retention slit that is configuredto hold a plurality of K-wires therein. The K-wires can be inserted andremoved by hand. The pliable silicone material allows individual K-wiresto be inserted or removed without disturbing the others in the sameslit. The K-wire holder 1110 further includes at least one attachmentfeature 1128 to attach the holder 1110 to a drape or other secure pointon the surgical table. By way of example, the attachment feature 1128 isa clip or clamp, however other attachment features are possible. Theattachment features 1128 are attached to the K-wire holder by way of acoiled ring 1130.

The techniques discussed herein present several challenges. One suchchallenge is being able to efficiently and effectively deliver aplurality of lock screws to successive bone anchors 12 while performingmulti-level fixation surgery. The multi-load lock screw inserterdescribed by way of example herein addresses this need by holding aplurality of lock screws simultaneously and providing for controlledsequential delivery of each lock screw to the target tulips beforehaving to reload the inserter with more lock screws. Instead of aspring, the multi-load lock screw inserter described herein utilizes athreaded mechanism to advance each successive lock screw into positionfor insertion. By using a threaded mechanism in lieu of a spring, theconstant distal force enacted by the spring is virtually removed andconsequently the force required to retain the lock screws on theinserter is much smaller. With a smaller retention force to overcome,intentional lock screw separation is much easier than with springmechanisms. As a result, the multi-load lock screw inserter describedherein will make lock screw delivery a faster process, saving thesurgeon valuable operating room time, thereby reducing the patient'srisk for infection.

FIGS. 162-169 illustrate an example of a multi-load lock screw inserter1150 configured to hold a plurality of lock screws 1152 simultaneouslyand thereafter facilitate controlled sequential delivery of each lockscrew to the target tulips 20 before having to reload the inserter withmore lock screws. By way of example the multi-load lock screw inserter1150 includes a handle 1154, rotating sleeve 1156, a threaded tube 1158,an inner shaft 1160, and a retention clip 1162.

The inner shaft 1160 has a distal tip geometry that mates with the lockscrews 1152. The inner shaft 1160 holds the lock screws 1152 and allowsthe user to deliver the lock screws 1152 to the bone anchors 12. Aretention clip 1162 is positioned near the distal tip 1164 of the innershaft 1160 and holds the lock screws 1152 onto the device, The retentionclip 1162 applies a frictional force on the inner diameter of the lockscrews 1152, which prevents the lock screws 1152 from accidentallyseparating from the device. The handle 1154 is attached to the innershaft 1160 to provide a means of applying torque. The threaded tube 1158is cannulated and receives the inner shaft 1160 therethrough. Thethreaded tube 1158 translates the lock screws 1152 distally and primesthe next lock screw for delivery. Limiter pins 1166 extend transverselythrough the inner shaft 1160 and engage the threaded tube 1158. Morespecifically, the limiter pins 1166 fit within an elongate channel 1168on the threaded tube 1158 and prevent rotation of the threaded tube 1158during translation. The rotating sleeve 1156 is coupled to the threadedtube 1158 and controls translation of the threaded tube 1158. Forexample, clockwise rotation of the rotating sleeve 1156 causes thethreaded tube 1158 to translate distally, and vice versa. The rotatingsleeve 1156 is held in place during rotation with a C-clip 1170. Athreaded spring ball detent 1172 gives the user tactile and audiblefeedback when the lock screw 1152 is in the proper position. The threadson the threaded tube 1158 are timed such that the lock screws 1152translate the distance of one lock screw for each 180° turn. Two holes1174 positioned opposite one another on the rotating sleeve 1156 allowspace for the threaded spring ball detent 1172 to engage; thus, givingthe user a tactile feel and an audible click to ensure the proper amountof rotation was achieved.

The rotating sleeve 1156 is cannulated and has an interior diameterlarge enough to receive the threaded tube 1158 therein. Two mating pins1176 are positioned opposite one another within the interior lumen ofthe rotating sleeve 1156 near the distal end. The mating pins 1176 areconfigured to engage the threaded portion 1178 of the threaded tube1158. Specifically, the mating pins 1176 fit within the thread channel1180 and translate along the thread channel 1180 when the rotatingsleeve 1156 is rotated. This translation of the mating pins 1176 alongthe thread channel 1180 in turn causes the threaded tube 1158 (whichdoes not rotate due to the limiter pins 1166) to then translate distally(in response to a clockwise rotation of the rotating sleeve 1156) orproximally (in response to a counterclockwise rotation of the rotatingsleeve 1156).

FIG. 167 illustrates the distal tip region of the multi-load lock screwinserter 1150 in greater detail, showing the distal tip region with nolock screws engaged. The inner shaft 1160 has a distal region geometrythat mates with the lock screws 1152. By way of example, the distalregion geometry is a hexalobe shape, however any geometry thatcomplements the geometry of the inserter lumen of the lock screw 1152may be used. The distal tip region further includes a retention clip1162 positioned within a clip recess 1182 formed circumferentially aboutthe inner shaft 1160 at the distal tip 1164. The retention clip 1162provides a physical barrier to prevent the lock screws 1152 fromaccidentally separating from the inserter, but allows passage of thelock screws if sufficient force is applied, The retention clip 1162 maybe composed of any material suitable to prevent unwanted release of thelock screws 1152. By way of example, the retention clip 1162 is made ofcobalt chrome. The threaded tube 1158 has an inner diameter large enoughto allow passage of the inner shaft 1160 therethrough but not the lockscrews 1152. As a result, the distal end 1184 of the threaded tube 1158engages with the lock screws 1152 and pushes them distally along theinner shaft 1160.

FIG. 168 is a close up view of the mating region of the rotating sleeve1156, inner shaft 1160, and silicone handle 1154, with the rotatingsleeve 1156 removed for clarity, The silicone handle 1154 is attached tothe proximal end of the inner shaft 1160 by any suitable attachmentmechanism. By way of example only, the proximal end of the inner shaftis provided with a threaded post 1186 that is threadedly received withina threaded aperture 1188 formed in the distal end of the silicone handle1154 (FIG. 166 ). When the silicone handle 1154 is rotated, the entireinstrument is in turn rotated and the lock screws 1152 may be advancedinto and secured within the screw tulip 20, The proximal portion of theinner shaft 1160 further includes a circumferential recess 1190configured to hold a C-clip 1170. The C-clip 1170 is positioned suchthat a portion of the C-clip resides within the circumferential recess1190 on the inner shaft 1160 and a second portion of the C-clip 1170resides in a corresponding circumferential recess on the inside lumen ofthe rotating sleeve 1156, thus securing the rotating sleeve 1156 to theinner shaft 1160 in such a way that the rotating sleeve 1156 is allowedto freely rotate about the axis defined by the inner shaft 1160, but isprevented from translating in any direction along that axis. Thethreaded spring ball detent 1172 is positioned at the proximal end ofthe inner shaft 1160 to give the user tactile and audible feedback whenthe lock screw 1152 is in the proper position at the distal end of theinner shaft 1160. The threaded spring ball detent 1172 comprises a ball1192 that is biased against the interior surface of the rotating sleeveby a spring (not shown). A pair of feedback apertures 1174 is positionedopposite one another on the proximal end of the rotating sleeve 1156 andfurther positioned such that rotation of the rotating sleeve 1156eventually brings the feedback aperture 1174 and threaded spring balldetent 1172 into alignment. When that happens, the ball 1192 is able topartially move into the feedback aperture 1174, giving the user tactileand audible feedback. The threads 1178 on the threaded tube 1158 aretimed such that the lock screws 1152 translate the distance of one lockscrew for each 180° turn of the rotating sleeve 1156. Thus, the tactileand audible feedback created by the interaction between the threadedspring ball detent 1172 and the feedback aperture 1174 is an indicationto the user that the lock screw 1154 has been fully advanced and isready to be engaged with the bone anchor 12.

FIG. 169 illustrates a sequential view of lock screw delivery into abone anchor. To use the multi-load lock screw inserter 1150 describedherein, the user would first load a plurality of lock screws 1152 (forexample up to 8 lock screws) onto the inner shaft 1160. To accomplishthis, the first step is to rotate the rotating sleeve 1156counterclockwise until the exposed inner shaft 1160 is the correctlength to accommodate the desired number of lock screws 1152. The secondstep is to insert the inner shaft 1160 through the desired number oflock screws 1152, making sure the last lock screw to be loaded isadvanced beyond the retention clip 1162 at the distal end 1164 of theinner shaft 1160. Next, as shown in FIG. 169 , the user can thread themost distal lock screw 1152 into a bone anchor 12 by rotating the entiredevice using the silicone handle 1154. When the lock screw 1152 and rod14 fully bottom out within the bone anchor 12, the multi-load lock screwinserter 1150 can be separated from the lock screw 1152 by pulling theinserter axially away from the bone anchor 12. Next, the user rotatesthe rotating sleeve 1156 180° clockwise to advance the next lock screw1152 into position. The proper position of the lock screw will beindicated by the tactile and audible feedback from the ball detent. Theprocess above is repeated until all lock screws have been delivered tobone anchors.

While the inventive features described herein have been described interms of a preferred embodiment for achieving the objectives, it will beappreciated by those skilled in the art that variations may beaccomplished in view of these teachings without deviating from thespirit or scope of the invention. Also, while this invention has beendescribed according to a preferred use in spinal applications, it willbe appreciated that it may be applied to various other uses desiringsurgical fixation, for example, the fixation of long bones.

What is claimed is:
 1. A minimally invasive surgical retractorcomprising: a first arm extending from a proximal end thereof to adistal end thereof along a first longitudinal axis; a second armconfigured to couple to the first arm, the second arm extending from aproximal end thereof to a distal end thereof along a second longitudinalaxis that is parallel to the first longitudinal axis; an actuationassembly configured to couple to the first arm and the second arm andfurther configured to cause the first arm and the second arm to rotaterelative to each other about a third longitudinal axis, wherein thethird longitudinal axis is parallel to the first longitudinal axis andthe second longitudinal axis; a first retractor blade configured tocouple to the distal end of the first arm; and a second retractor bladeconfigured to couple to the distal end of the second arm.
 2. Theretractor of claim 1, wherein the second arm is configured to hingedlycouple to the first arm about the third longitudinal axis.
 3. Theretractor of claim 1, wherein the first arm comprises a first centralportion between the proximal end of the first arm and the distal end ofthe first arm.
 4. The retractor of claim 3, wherein the first centralportion comprises a flange that laterally extends toward the second armand is configured to be received within a flange recess of the secondarm.
 5. The retractor of claim 4, wherein the flange comprises a hingeaperture extending along the first longitudinal axis, wherein the hingeaperture is sized to receive a pivot pin therein for securing the flangeto the flange recess.
 6. The retractor of claim 3, wherein the firstcentral portion comprises a recess formed in an underside of the firstarm.
 7. The retractor of claim 6, wherein the second arm comprises aprotrusion laterally extending toward the first arm and configured to bereceived within the recess of the first central portion.
 8. Theretractor of claim 7, wherein the actuator assembly comprises a mountingunit configured to be received within the recess of the first centralportion and coupled to the protrusion of the second arm.
 9. Theretractor of claim 6, wherein the first central portion furthercomprises an aperture formed in the top surface of the first centralportion, wherein a lip of the aperture forms an overhang.
 10. Theretractor of claim 9, wherein the actuator assembly further comprises anactuator comprising: a head configured to be actuated by a drive tool;an upper lip configured to contact an upper surface of the overhang; alower lip configured to contact an underside of the overhang; and acircumferential recess extending between the upper lip and the lowerlip, wherein the circumferential recess is configured to mate with theaperture.
 11. The retractor of claim 3, wherein the first centralportion comprises a button aperture sized to house a blade releasebutton therein.
 12. The retractor of claim 11, wherein the blade releasebutton comprises: a button head; a post extending distally below thebutton head; and an upper-facing ridge forming a catch at a distal endof the post, wherein the catch is configured to interact with acomplementary catch of the first retractor blade.
 13. The retractor ofclaim 12, wherein the blade release button further comprises a springconfigured to bias the blade release button to releasably engage thecatch of the blade release button with the catch of the first retractorblade.
 14. The retractor of claim 1, wherein the distal end of the firstarm comprises a blade aperture configured to couple to the firstretractor blade.
 15. The retractor of claim 1, wherein the proximal endof the first arm comprises a threaded aperture sized to receive a firstattachment ring.
 16. The retractor of claim 15, wherein the firstattachment ring is configured to engage with an independent instrument.17. The retractor of claim 16, wherein the independent instrument is aninsertion handle or a mounting device.
 18. A method comprising:providing a surgical retractor comprising: a first arm extending along afirst longitudinal axis, a second arm extending along a secondlongitudinal axis that is parallel to the first longitudinal axis, anactuation assembly, a first retractor blade, and a second retractorblade; coupling the first arm and the second arm about a thirdlongitudinal axis, wherein the third longitudinal axis is parallel tothe first longitudinal axis and the second longitudinal axis; couplingthe first retractor blade to a distal end of the first arm; coupling thesecond retractor blade to a distal end of the second arm; coupling theactuation assembly to the first and second arms; actuating the actuationassembly, thereby causing the first retractor blade and the secondretractor blade to rotate relative to each other about the thirdlongitudinal axis.
 19. The method of claim 18, wherein the coupling thefirst arm and the second arm further comprises hingedly coupling thefirst arm and the second arm about the third longitudinal axis.
 20. Themethod of claim 18, wherein the actuation assembly comprises an actuatorunit and a mounting unit configured to threadedly couple to the actuatorunit, and the actuating the actuation assembly further comprises:rotating the actuator unit; and laterally translating the mounting unitand causing the first arm and the second arm to rotate relative to eachother about the third longitudinal axis.